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Old 12-03-2012, 10:31 PM   #1
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


I'm on the final countdown to replacing my gas valve on my furnace (probably should use a less explosive word than "countdown"!) and the helpful people in this forum who know stuff might be amused at my "Safe Steps" below, but a quicker read option is just to pipe-in on the following two questions:

1. Black Iron pipe or Black Steel pipe for my two pieces out of the valve and out the side of the furnace? One store has steel, the other iron, and both say they are for gas, and they may both be manufactured by "LDR". The pipe inside the furnace looks to be brass (would assume it's not copper) and I'll be replacing the same brass-looking pipe to run to my gas line.

2. The yellow type of Teflon Tape, pipe dope, or an even higher quality of Teflon Tape? I imagine this could venture into just people's preference, but I'm hoping to use teflon tape for all threaded connections (except the "fitted ones" like the shut-off valve and the kinda flexible gas connector line, probably by BrassCraft). At the parts store (gas valve) I'll ask about Red Teflon Tape which the internets shows as a step up from the yellow. Yellow is the best the hardware stores have.

Thanks, and for more amusement or anyone's further consideration, read on below.

Rich

If anyone cares to see the steps I plan to do, I list them here in case there's something dumb that could be caught ahead of time.

Uh, a brief explanation of why I'm doing this: old gas valve's pilot valve is sticking on sometimes

Safe Steps

A. With furnace off (valve turned off inside the furnace, unplugged, gas shut-off valve outside the furnace on gas input line turned to off), turn off water heater (has a standing pilot) and close its gas input shut-off valve as well.

B. Disconnect the pilot tubing from the old gas valve and remove the pilot assembly (as well as its two electric thingies - one like an old soldering iron end that is likely a glow bar for lighting, the other a sensor to make sure the pilot is lit). Of course disconnect each of those two electronically from the Ignition Control (RobertShaw SP 715A) - where one connects to "Ign." and the other to "Sensor"...

C. Sniff pilot gas outlet. Old valve and the gas in-line shut-off both being off makes it super unlikely that there can be an issue with that leaking, but be safe as can be.

D. Pop over to the parts store. Buy the replacement gas valve (RobertShaw 720-070) and hopefully two new pieces (sensor and "glow bar" lighter) to fit into my existing pilot assembly, and possibly a new pilot fitting. I'm thinking now that if replacing anything means the pilot assembly has to be replaced and I cannot use the existing bracket/sheet metal stuff to mount the pilot, I'll likely just clean up mine with some steel wool 'cuz I don't want to get into trying to do sheet metal and bracket type work to put in a new anything there. A sensor and "glow bar" that will work exactly with what I've got? Great, why not. And I reckon I will need new pilot light tubing, but the parts folks will advise me on that.

E. Buy other stuff (black iron/steel pieces for going out the furnace from the new gas valve, BrassCraft flexish piece to run from in-line shut-off valve to black pipe, paranoia terminate plug as described in the next step, better grade Teflon tape than Yellow if available) and return home.

F. Have on hand one valve plug (fitted like connector for BrassCraft gas connector line, but terminates the flow) in case once I remove the gas connector line with the in-line shut-off valve turned off, it turns out the shut-off valve for the furnace leaks. It's not leaking anywhere else, but how do I know if the ball valve isn't actually letting gas through the line since all has been hooked up beyond the valve each time I've had it turned off? Establishing the shut-off is good is something I'll do just with my nose. (This is a plan B to turning off the gas at the meter outside 'cuz that looks like a big to-do, all painted over, etc. I do plan to avail myself of our gas company's service to check out furnaces and gas connections when done, so I'll ask the guy about that meter shut-off and if it should totally work if I need it to, for future disaster reference.)

G. Disconnect old connector line from the in-line shut-off valve. (step F at the ready above if I smell any gas, and that would be to first reconnect, but if gas is leaking thru the closed valve AND my moving the old not-so-flexible-anymore connector line means it too is going to leak, then I have that valve "plug")

H. Disconnect the connector line entirely, then the old gas valve (with straight pipe and elbow pipe still connected to its main input, being aware that in so doing no torque should be applied to the other side - gas pipe to burners - of the old gas valve. Probably just hold the inside-the-furnace main burner gas pipe with a pipe wrench and turn the old gas valve itself, with its input pipe and elbow still attached. Uh, all the wires would already be disconnected and labeled - or colors noted - for reconnecting to the new gas valve...

I. Carefully brush/maybe steel wool the threads of the inside-the-furnace gas pipe that the new gas valve will go onto... Pipe dope was used and have to cleanly get it off of there while keeping the threads in as good of condition as possible.

J. Probably hook up the pilot at this point and some "flashing" that kind of blocks the gas valve from the direct heat of the burners...

K. With Yellow Teflon Tape (or Red if the parts store has that) turn the new gas valve onto the furnace gas line (that goes to burners) - my old gas valve is exactly upside down and I've been told that gas valves function fine any way they end up once tightened onto the threads of the gas pipe going to the burners. Good front access to the on/off lever would be nice, but I don't think I have any control there.

L. Connect a new black iron or black steel pipe piece (mpt each end) that will probably be roughly the same length as the old brass colored pipe piece, probably with an "elbow" (fpt both sides) already connected, as well as an mpt to mpt converter connected to the input end of the elbow. These connections all using the teflon tape, and the one to the gas valve tightened holding the gas valve itself firmly as not to put any torque on the outtake side already connected.

M. Connect the new BrassCraft connector between the in-line gas input shut-off valve and the mpt sticking out from the elbow. Not sure if both of these will be "no teflon tape or pipe dope", but I think at least the connector to the shut-off valve is fitted, and those fitted connections don't use teflon tape or pipe dope.

N. All wires back on to the proper ignition control terminals from the pilot lighter and heat sensor, as well as the wires to the new gas valve terminals (which do match the old gas valve terminals).

O. Now the fun part. Furnace still unplugged and new gas valve turned off, open the in-line gas input shut-off valve having my nose twitching like a rabbit's and using my little spray bottle of soapy water (dish soap mixed with water is what I've read) on all the connections up to all but the connection to the gas valve, confirm that nothing is leaking up to there.

P. At the gas valve input pipe connection I'll use soapy water to test, but likely by using a Q-tip (imagine "R" registered trademark symbol here for "Q-tip") to apply the soapy water all around the new gas valve connection. (More control and no overspray - don't want to get soapy water onto much else than the connection point... Probably be wiping off the soapy water with wet rag after each test inside the furnace...)

Q. If all still seems good, then with the thermostat all the way down (already would be), plug in the furnace and turn the new gas valve lever to On, nose a-twitchin'... Of course gas shouldn't be any further to any other connections, so go turn the thermostat up to fire it up and return quickly. (Hmmm... Maybe think "start it up" rather than "fire it up"?)

R. R but Q for Q-tip again? As then I'd check with soapy water the last of the connections in the loop, the main burner pipe out from the gas valve and the pilot line out from the gas valve. (Hmmm... Could do this with the main burner wire off, and just test the pilot connection first without the burners coming on yet? Then if pilot connection is good, do it again but with the main burner wire back on?)

S. Any non-functioning aspects past that - I'll have the multimeter to test for voltage where it should be, etc.

T. Expectation is that then watching regular usage closely (or actually causing it by adjusting the thermostat), all should shut off every time (including the pilot), and turn on every time, pilot first, then burners after a bit.

U. At my "trail wife's" request (we're backpackers - and yes, I think her request is smart, too), once all done I'd probably continue like I have been (use the furnace kind of manually - turning down the thermostat all the way, turn off the gas valve, turn off the shut-off gas valve on the gas to the furnace, and unplug the furnace) overnight as well as during the day when I'm out or at work, and do have the gas company come out when their and my schedule can accommodate, to have them check it all out. If that is something they don't do anymore, then, uh, just watch it closely for a time, do a lot of sniffing, and eventually feel comfortable that I did it right. Oh, and yes, I'd turn on the water heater gas valve and light that standing pilot once all the work was done and I'd verified no gas leaks.

Sorry that turned out so enormous! I almost ran out of the alphabet. I did think this would be just a short number of simple looking steps, but I will be using it myself, and I do like to have a full plan. If anyone does read any of it and spots something that seems iffy, please do let me know.

Thanks,

Rich Apple

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Old 12-03-2012, 10:35 PM   #2
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


pipe dope

Black Iron pipe

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Old 12-03-2012, 11:26 PM   #3
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


I've seen IOM's shorter than that.
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Old 12-03-2012, 11:32 PM   #4
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


Black iron pipe
yellow gas approved tape and/or gas approved pipe dope. Do not apply it on first 3 threads.
And I didn't read the rest..........
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Old 12-04-2012, 12:03 AM   #5
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


Thanks for the first three threads advice, EPlumber, and NiNe O, I'm not sure what an IOM is, but guessing one is often long, meticulous, and boring!

Thanks...

Rich

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Old 12-04-2012, 12:04 AM   #6
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


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Originally Posted by richapple View Post
I'm on the final countdown to replacing my gas valve on my furnace (probably should use a less explosive word than "countdown"!) and the helpful people in this forum who know stuff might be amused at my more like morally obligated to see if your are going to blow yourself up "Safe Steps" below, but a quicker read option is just to pipe-in on the following two questions:

1. Black Iron pipe or Black Steel pipe for my two pieces out of the valve and out the side of the furnace? Why does it take two pieces? no unions in a burner compartment One store has steel, the other iron, and both say they are for gas, and they may both be manufactured by "LDR". The pipe inside the furnace looks to be brass (would assume it's not copper) and I'll be replacing the same brass-looking pipe to run to my gas line.

2. The yellow type of Teflon Tape, pipe dope, or an even higher quality of Teflon Tape? I imagine this could venture into just people's preference, but I'm hoping to use teflon tape for all threaded connections (except the "fitted ones" like the shut-off valve and the kinda flexible gas connector line, probably by BrassCraft). At the parts store (gas valve) I'll ask about Red Teflon Tape which the internets shows as a step up from the yellow. Yellow is the best the hardware stores have. Use any pipe sealant rated for ng or lp whatever ya got, throw a dart, just check for leaks.

Thanks, and for more amusement or anyone's further consideration, read on below.

Rich

If anyone cares to see the steps I plan to do, I list them here in case there's something dumb that could be caught ahead of time.

Uh, a brief explanation of why I'm doing this: old gas valve's pilot valve is sticking on sometimes

Safe Steps

A. With furnace off (valve turned off inside the furnace, unplugged, gas shut-off valve outside the furnace on gas input line turned to off), turn off water heater (has a standing pilot) and close its gas input shut-off valve as well. Technically, you should probably run a call for heat and then shut the supply gas cock off and let the thing burn off the remaing gas in the manifold, you know, "to be safe"

B. Disconnect the pilot tubing from the old gas valve and remove the pilot assembly (as well as its two electric thingies - one like an old soldering iron end that is likely a glow bar for lighting it's an ignitor and do not touch, ever, the other a sensor to make sure the pilot is lit flame sensor, clean with brillo pad). Of course disconnect each of those two electronically from the Ignition Control (RobertShaw SP 715A) - where one connects to "Ign." and the other to "Sensor"...Use a pair of needle nose pliers, grip connector perpindicular and wiggle a little then using the module for leverage, pop off connector, you can break connectors or solder joints in the board.

C. Sniff pilot gas outlet . Old valve and the gas in-line shut-off both being off makes it super unlikely that there can be an issue with that leaking, but be safe as can be. I have no idea why you would do this other than you just like getting your rocks of sniffin' stuff.

D. Pop over to the parts store. Buy the replacement gas valve (RobertShaw 720-070) and hopefully two new pieces (sensor and "glow bar" lighter) to fit into my existing pilot assembly, and possibly a new pilot fitting. I'm thinking now that if replacing anything means the pilot assembly has to be replaced and I cannot use the existing bracket/sheet metal stuff to mount the pilot, I'll likely just clean up mine with some steel wool 'cuz I don't want to get into trying to do sheet metal and bracket type work to put in a new anything there. A sensor and "glow bar" that will work exactly with what I've got? Great, why not. And I reckon I will need new pilot light tubing, but the parts folks will advise me on that. Why not just by the valve ahead of time with a few different sized nipples that you think will get the job done. Unless the pilot is all sooted up and impossible to clean I'd keep it. Ohm out the ignitor to see if its bad. keep a good one handy but don't replace if not necessary.

E. Buy other stuff (black iron/steel pieces for going out the furnace from the new gas valve, BrassCraft flexish piece to run from in-line shut-off valve to black pipe, paranoia terminate plug as described in the next step, better grade Teflon tape than Yellow if available) and return home. most hardwares will cut the pipe any size you want, use some of this energy to make a plan for piping, by the fittings and nipples and save yourself the embarrassment of having a movable appliance gas connector on your immovable furnace.

F. Have on hand one valve plug (fitted like connector for BrassCraft gas connector line, but terminates the flow) in case once I remove the gas connector line with the in-line shut-off valve turned off, it turns out the shut-off valve for the furnace leaks. It's not leaking anywhere else, but how do I know if the ball valve isn't actually letting gas through the line since all has been hooked up beyond the valve each time I've had it turned off? Establishing the shut-off is good is something I'll do just with my nose. (This is a plan B to turning off the gas at the meter outside 'cuz that looks like a big to-do, all painted over, etc. I do plan to avail myself of our gas company's service to check out furnaces and gas connections when done, so I'll ask the guy about that meter shut-off and if it should totally work if I need it to, for future disaster reference.) Use bubble for leaks, once you take the piping apart all you'll smell is gas, your wife will come down and tell you she smells, the dog will leave the room, but thats good, thats what it's suppose to do.

G. Disconnect old connector line from the in-line shut-off valve. (step F at the ready above if I smell any gas, and that would be to first reconnect, but if gas is leaking thru the closed valve AND my moving the old not-so-flexible-anymore connector line means it too is going to leak, then I have that valve "plug") You are going to know if that gas cock leaks after you loosen the first fitting no need for a back up plan. You say you don't want to touch that meter outside, what if something does go wrong, you better make sure you can shut it off there.

H. Disconnect the connector line entirely, then the old gas valve (with straight pipe and elbow pipe still connected to its main input, being aware that in so doing no torque should be applied to the other side - gas pipe to burners - of the old gas valve. Probably just hold the inside-the-furnace main burner gas pipe with a pipe wrench and turn the old gas valve itself, with its input pipe and elbow still attached. Uh, all the wires would already be disconnected and labeled - or colors noted - for reconnecting to the new gas valve...

I. Carefully brush/maybe steel wool the threads of the inside-the-furnace gas pipe that the new gas valve will go onto... Pipe dope was used and have to cleanly get it off of there while keeping the threads in as good of condition as possible.

J. Probably hook up the pilot at this point and some "flashing" that kind of blocks the gas valve from the direct heat of the burners...

K. With Yellow Teflon Tape (or Red if the parts store has that) turn the new gas valve onto the furnace gas line (that goes to burners) - my old gas valve is exactly upside down and I've been told that gas valves function fine any way they end up once tightened onto the threads of the gas pipe going to the burners. Good front access to the on/off lever would be nice, but I don't think I have any control there.

L. Connect a new black iron or black steel pipe piece (mpt each end) that will probably be roughly the same length as the old brass colored pipe piece, probably with an "elbow" (fpt both sides) already connected, as well as an mpt to mpt converter connected to the input end of the elbow. These connections all using the teflon tape, and the one to the gas valve tightened holding the gas valve itself firmly as not to put any torque on the outtake side already connected.


Thanks,

Rich Apple
I quit reading and believe you are not comfortable in yourself to get this done. This is a 45 minute job hard piped, and 25 minutes with a flex connector. This is gas, it is dangerous, your plan is no good, IMO, and you really have no idea what your are talking about through much of this.
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Old 12-04-2012, 12:04 AM   #7
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


Pipe dope and black iron. You'll also need to check manifold pressure, clock your furnace to determine correct input, check temp rise and check the draft if it's a natural draft- I skimmed.
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Old 12-04-2012, 12:07 AM   #8
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


Oh yeah, one more thing: don't rely on your nose alone to detect a leak. The more you smell gas, the less readily you are able to detect it.
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Old 12-04-2012, 12:10 AM   #9
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


I kept reading and learned your old valve is upside down, this is more thank likely why the pilot won't close. Don't do this again.
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Old 12-04-2012, 03:36 AM   #10
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


Well, I'd like to update this with some specific replies. I had not thought of the aspect NiNe O pointed out with his "more like morally obligated to see if your are going to blow yourself up" to my suggestion that looking at my plan might be amusing to people who know this biz, so I apologize to anyone who saw it that way.

For the things I don't know (HVAC Benny's "need to check manifold pressure, clock your furnace to determine correct input" as an example), my thinking had been that the furnace works just fine now with the existing valve, so replacing with what RobertShaw says is the "exact" replacement should be fine and the existing input wouldn't change and would be correct). Granted I would not have been tuning/servicing my furnace the way a good professional will, but it would work as efficiently as it does now after my gas valve swap. Where I now see I'm likely wrong is that a new gas valve out of the box may not meet what my old valve had been adjusted to...

NiNe O - thank you for taking quite a bit of time, and I'll try a few particular replies (without quoting the context) out of respect for you taking that time.

Running a call for heat and cutting the gas supply to burn off what is in the manifold: Brilliant, and I had considered the leftover gas in the pipes alone and how I'd smell that upon opening anything up. I would suppose the cutting off of the gas during a "call for heat" may or may not clear that (gas lingering between the shut-off valve and the furnace gas valve, for instance, may remain because gas pressure is not pushing it thru).

Do not touch ignitor ever: If that means that even without power to it and after plenty of time to cool the ceramic-looking lower part under the glow bar part (again, looks like a soldering iron to me) can retain some sort of charge and be somehow dangerous to the touch, well that doesn't seem likely to me, so I likely misunderstand you. I was talking about taking this and all the pilot stuff to the parts store, so yeah, I would be probably touching it.

Clean flame sensor with Brillo Pad: My plan had me, if reusing that one, to yes clean it. I was going to use steel wool which, unlike a Brillo Pad, doesn't have soap.

Needle nose pliers for careful removal of connectors: Very good advice always, and as someone who has done electronics, something I did already know.

No idea why I'd sniff the pilot valve opening: Enjoyed the humor yes, but leaving the house with having every bit of evidence that nothing is now leaking out of the one opening into the gas corridors I've opened up wouldn't seem smart. Sniffing seemed to be the only way - and yes, HVAC Benny's post... I get now that especially with some residual gas odors that might be there at first, at some point my sniffer is not going to be the best judge anyway.

Buy the valve ahead of time and keep the pilot: The beginnings of all of this for me (how I found the pilot was staying on sometimes) was that some winters when first putting up the thermostat my furnace would fail to start because the flame sensor had slipped out of position and was not in the flame. Unable to even see anything, I've always been able to reach behind (with the thermostat down and enough time passed for it all to be cooled) and bring that up into position. This year the furnace was not coming on and yet the flame sensor had not slipped out of position. (Not sure why the flame sensor tends to stay in position for the rest of the heat-needing part of the year.) Anyway, after the tiniest bit of cleaning (just reaching back there) it has now continued to function perfectly, but taking the entire pilot assembly with me to the parts store when I buy the gas valve to see if a new one was available seemed a good idea.

Ohm out the ignitor to see if it's bad: I think you're getting into Buddhism now and that is kinda beyond me. ("Om" reference, humor attempt) But to be honest, I'm a little lost on this one 'cuz though I measured the 24 volts that get sent from the ignition control (I think the same goes to the pilot valve terminal and via another wire to the ignitor), I assume you're talking about testing it independently of "Does it light the pilot".

Get pipe cut to size and eliminate the moveable appliance gas connector: Yes, that sounds pro and smart, and my guess is that the industry people who installed it, not to mention the professional plumber who a couple years ago installed a new water heater, use these moveable gas appliance gas connectors because they are convenient and faster?

Loosen the first fitting and I'll know if the shut-off valve leaks, so no need for back-up plan, and shouldn't the ultimate backup plan be to shut the gas off at the main valve? (You've probably noticed I'm paraphrasing with these): True that. I should make sure I can shut that off anyway, and yeah I've got the where-with-all to do so and should.

(** Update and Oooops ** - the old valve is not upside down and I was considering the writing on turning On/Off knob wrong. Though the replacement valve probably would turn onto the threads and end up right-side up too, for other reasons given I'm still backing off doing this myself... **) Old: As for the old valve being upside down, unless the adage is "yes, after 23 years an upside down gas valve could start having its valves stick open", I kind of think that's not the reason. The York furnace came that way, new in the house when I moved in - or perhaps the furnace business is that a local HVAC place puts them together for installations and they did it that way. I was told by the parts place that a gas valve does not have to be level or upright, but I see at the RobertShaw site that they should not be mounted upside down. Bottom line is that when my house was built the contractor seemed quite earnest to cut corners, and perhaps the upside down furnace gas valve and movable gas appliance connectors are a sign of that.

Epilogue: I started down this path because I was curious and wanted to debug my furnace problem (pilot staying lit sometimes), and then, partly with some hints from another post to this forum, I finally did debug it. (First proof to me that it was a stuck pilot valve in the combination gas valve was when I found that a tap on the combination valve let the pilot valve close and the pilot go out - then it took days of back and forth to the garage after heater shut-downs to have it happen again so I could test with the multimeter to see: yes, pilot light on, and no, 24 volt charge not there between Common and Pilot terminals on the valve assembly.)

Once I knew why, the puzzle was gone and my interest level dropped a bit, but I still felt a certain momentum and that I should fix it myself. The stated fact that a gas valve should not be mounted upside down (and I figure just as much it shouldn't be tilted) changes this for me. Having the gas valve upright can only mean that one can't do this as I envisioned (not having to do anything with the main outflow gas pipe that is built into the furnace, curved, and not something I can see me messing with). The gas valve turning onto the threads of that outflow gas pipe I'm seeing as absolutely fixed inside the furnace is very very likely to not end up upright when fully tightened.

So end of story, and while for all my words a bunch of self-doubt could have been interpreted for what I was thinking I could do (safely control the gas sitch to swap out the existing gas valve and turning a new one onto that "fixed" outflow gas pipe inside the furnace), that self-doubt or my not feeling comfortable for doing that work myself wasn't the case. There are probably a lot of HVAC professionals here like NiNe O and the skills/knowledge of that trade go far beyond the simple wrench-jockey steps I was planning to do... And yes, while I do think I could have accomplished what I was going to do, the result could easily have been a less-correctly running furnace with proper pressure settings, etc.

Again, sorry if my putting my plan into words (and yes, too many words, as is my style) seemed to be asking anyone to feel morally obligated to review and advise or this guy in California is going to blow himself to high heaven. I was just looking to get the most input (and obviously I've been a bit obsessed with it). It's not like I can't afford to have a professional do the complete job and consider all the aspects beyond my basic gas-valve-swap theory, and for that I'll end up with a better furnace servicing for sure.

Thanks all, and I look forward to using this forum for much simpler, direct this-or-that questions in the future (though probably usually just finding my answers via searches). Seems like a good, active bunch of members...

Last edited by richapple; 12-04-2012 at 06:51 PM.
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Old 12-04-2012, 06:36 AM   #11
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


Quote:
Originally Posted by richapple View Post
Well, I'd like to update this with some specific replies. I had not thought of the aspect NiNe O pointed out with his "more like morally obligated to see if your are going to blow yourself up" to my suggestion that looking at my plan might be amusing to people who know this biz, so I apologize to anyone who saw it that way.

For the things I don't know (HVAC Benny's "need to check manifold pressure, clock your furnace to determine correct input" as an example), my thinking had been that the furnace works just fine now with the existing valve, so replacing with what RobertShaw says is the "exact" replacement should be fine and the existing input wouldn't change and would be correct). Granted I would not have been tuning/servicing my furnace the way a good professional will, but it would work as efficiently as it does now after my gas valve swap. Where I now see I'm likely wrong is that a new gas valve out of the box may not meet what my old valve had been adjusted to...

NiNe O - thank you for taking quite a bit of time, and I'll try a few particular replies (without quoting the context) out of respect for you taking that time.

Running a call for heat and cutting the gas supply to burn off what is in the manifold: Brilliant, and I had considered the leftover gas in the pipes alone and how I'd smell that upon opening anything up. I would suppose the cutting off of the gas during a "call for heat" may or may not clear that (gas lingering between the shut-off valve and the furnace gas valve, for instance, may remain because gas pressure is not pushing it thru).

Do not touch ignitor ever: If that means that even without power to it and after plenty of time to cool the ceramic-looking lower part under the glow bar part (again, looks like a soldering iron to me) can retain some sort of charge and be somehow dangerous to the touch, well that doesn't seem likely to me, so I likely misunderstand you. I was talking about taking this and all the pilot stuff to the parts store, so yeah, I would be probably touching it.

Clean flame sensor with Brillo Pad: My plan had me, if reusing that one, to yes clean it. I was going to use steel wool which, unlike a Brillo Pad, doesn't have soap.

Needle nose pliers for careful removal of connectors: Very good advice always, and as someone who has done electronics, something I did already know.

No idea why I'd sniff the pilot valve opening: Enjoyed the humor yes, but leaving the house with having every bit of evidence that nothing is now leaking out of the one opening into the gas corridors I've opened up wouldn't seem smart. Sniffing seemed to be the only way - and yes, HVAC Benny's post... I get now that especially with some residual gas odors that might be there at first, at some point my sniffer is not going to be the best judge anyway.

Buy the valve ahead of time and keep the pilot: The beginnings of all of this for me (how I found the pilot was staying on sometimes) was that some winters when first putting up the thermostat my furnace would fail to start because the flame sensor had slipped out of position and was not in the flame. Unable to even see anything, I've always been able to reach behind (with the thermostat down and enough time passed for it all to be cooled) and bring that up into position. This year the furnace was not coming on and yet the flame sensor had not slipped out of position. (Not sure why the flame sensor tends to stay in position for the rest of the heat-needing part of the year.) Anyway, after the tiniest bit of cleaning (just reaching back there) it has now continued to function perfectly, but taking the entire pilot assembly with me to the parts store when I buy the gas valve to see if a new one was available seemed a good idea.

Ohm out the ignitor to see if it's bad: I think you're getting into Buddhism now and that is kinda beyond me. ("Om" reference, humor attempt) But to be honest, I'm a little lost on this one 'cuz though I measured the 24 volts that get sent from the ignition control (I think the same goes to the pilot valve terminal and via another wire to the ignitor), I assume you're talking about testing it independently of "Does it light the pilot".

Get pipe cut to size and eliminate the moveable appliance gas connector: Yes, that sounds pro and smart, and my guess is that the industry people who installed it, not to mention the professional plumber who a couple years ago installed a new water heater, use these moveable gas appliance gas connectors because they are convenient and faster?

Loosen the first fitting and I'll know if the shut-off valve leaks, so no need for back-up plan, and shouldn't the ultimate backup plan be to shut the gas off at the main valve? (You've probably noticed I'm paraphrasing with these): True that. I should make sure I can shut that off anyway, and yeah I've got the where-with-all to do so and should.

As for the old valve being upside down, unless the adage is "yes, after 23 years an upside down gas valve could start having its valves stick open", I kind of think that's not the reason. The York furnace came that way, new in the house when I moved in - or perhaps the furnace business is that a local HVAC place puts them together for installations and they did it that way. I was told by the parts place that a gas valve does not have to be level or upright, but I see at the RobertShaw site that they should not be mounted upside down. Bottom line is that when my house was built the contractor seemed quite earnest to cut corners, and perhaps the upside down furnace gas valve and movable gas appliance connectors are a sign of that.

Epilogue: I started down this path because I was curious and wanted to debug my furnace problem (pilot staying lit sometimes), and then, partly with some hints from another post to this forum, I finally did debug it. (First proof to me that it was a stuck pilot valve in the combination gas valve was when I found that a tap on the combination valve let the pilot valve close and the pilot go out - then it took days of back and forth to the garage after heater shut-downs to have it happen again so I could test with the multimeter to see: yes, pilot light on, and no, 24 volt charge not there between Common and Pilot terminals on the valve assembly.)

Once I knew why, the puzzle was gone and my interest level dropped a bit, but I still felt a certain momentum and that I should fix it myself. The stated fact that a gas valve should not be mounted upside down (and I figure just as much it shouldn't be tilted) changes this for me. Having the gas valve upright can only mean that one can't do this as I envisioned (not having to do anything with the main outflow gas pipe that is built into the furnace, curved, and not something I can see me messing with). The gas valve turning onto the threads of that outflow gas pipe I'm seeing as absolutely fixed inside the furnace is very very likely to not end up upright when fully tightened.

So end of story, and while for all my words a bunch of self-doubt could have been interpreted for what I was thinking I could do (safely control the gas sitch to swap out the existing gas valve and turning a new one onto that "fixed" outflow gas pipe inside the furnace), that self-doubt or my not feeling comfortable for doing that work myself wasn't the case. There are probably a lot of HVAC professionals here like NiNe O and the skills/knowledge of that trade go far beyond the simple wrench-jockey steps I was planning to do... And yes, while I do think I could have accomplished what I was going to do, the result could easily have been a less-correctly running furnace with proper pressure settings, etc.

Again, sorry if my putting my plan into words (and yes, too many words, as is my style) seemed to be asking anyone to feel morally obligated to review and advise or this guy in California is going to blow himself to high heaven. I was just looking to get the most input (and obviously I've been a bit obsessed with it). It's not like I can't afford to have a professional do the complete job and consider all the aspects beyond my basic gas-valve-swap theory, and for that I'll end up with a better furnace servicing for sure.

Thanks all, and I look forward to using this forum for much simpler, direct this-or-that questions in the future (though probably usually just finding my answers via searches). Seems like a good, active bunch of members...
gas , gas valves ARE NOT DIY PROJECTS>.i did not read post don't have that much time.....because of the danger..pros have to be licensed....as far as valve being direct replacement.. never assume that.need to check incomming gas pressure....manifold out pressure and the valve safety....even new parts are bad..ben sr
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richapple (12-04-2012)
Old 12-04-2012, 06:37 AM   #12
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


I skimed most of this too, Sorry. There is no "Iron" pipe used in gas supplies. Iron is more of a general term that the actual type. All gas pipe sold is black painted steel seamless pipe. Iron does not cut and thread the way steel does.

The reason you do not touch the igniter is that finger oils can shorten the life span.

Pipe dope, not tape. My preference.
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Old 12-04-2012, 12:44 PM   #13
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


As the guys have mentioned gas valves are not preset. Input and output must be measured. An exact replacement means the electrical components and opening speeds are the same. I've never seen one come out of the box set correctly.
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Old 12-05-2012, 11:33 AM   #14
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A couple furnace gas pipe questions, and an entire plan to replace my gas valve


Now I know why HVAC technicians usually tell people to call a tech. This is not meant to be an insult. Based on the terminology you use, and how you use it, you should not go anywhere near anything that is flammable, explosive, or carries a current large enough to kill you.

You are not a mechanic, so don't try to be one. Do what you do best, and leave mechanical things to the mechanically inclined.

For the record, Black Pipe in the smaller diameters such as used for gas supply is made of mild Steel, so is Galvanized pipe, which is simply Black pipe that has been coated with zinc.

There is Cast Iron pipe that comes in large sizes used for drain waste vent DWV applications, but the stuff you are using is mild steel. At one time it was thought that natural gas would cause the galvanizing inside galvanized pipe to flake off and clog gas lines. That was debunked many many years ago as being false, but some people still go by this fallacy. In many locales either can be used for gas.

Using the term black iron is like using the nomenclature CDX with reference to plywood. That meant C face veneer, D back veneer, and Exterior glue.

All Plywood has used exterior glue since the late 60's. The correct terminology is CD-Exposure 1, but that goes to show you how long improper definitions and myths can hang around, especially to those that refuse to read, keep themselves informed, or only learn by hearsay.

For what its worth, I would always use pipe dope when joining gas pipe. The threads that are cut on gas pipe are kind of crude due to the material being used. Some guys use both tape and dope. I use only Teflon pipe dope, only on the male end, and kept back from the end of the pipe about 3/16"

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