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Old 01-29-2009, 09:45 PM   #1
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Gasing a Tankless Water Heater


Had a Paloma PTG-74PVN-2 Tankless Water Heater put in and I am now in need of input regarding a comment I received from a different installer. It was suggested that the 3/4" line running to the unit should have come off of the incoming line before the regulator. And then, a second regular be installed right at the unit between the corrugated stainless steel (css) line and the unit. He said the water heater may fail (not run optimally) due to the gas useage (requirement). It has been installed for a couple of weeks and don't know enough about diagnosing optimal vs. just "ok" performance. The current configuration seems to be working for us. Does it need reconfigured???

The two photos show the config. now. 3/8 copper from outside meter (2psi), comes in from upper right, 1/2" black pipe, through regulator, manifold (this is where the yellow 3/4 css line runs to unit), 1/2" to furnace on lower left. the second photo is of the css running direct to unit.
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Old 01-30-2009, 05:08 AM   #2
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Gasing a Tankless Water Heater


Yep, kind of defeats the purpose of having a 2pound supply.

Plus, that is the just about the worst place you could put teh regulator and manifold.

Adds lots of time to cleaning the A/C coil down the road.

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Old 01-30-2009, 07:46 AM   #3
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Gasing a Tankless Water Heater


Quote:
3/8 copper from outside meter
Ayuh,....

I would think the 3/8" copper is going to be the Restriction....
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Old 01-30-2009, 07:56 AM   #4
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Gasing a Tankless Water Heater


If you had tapped the 2lb side of the regulator for the water heater, you'd need another regulator on the CSST line...Can't run 2lbs to an appliance so you'd have to bump that pressure down. Hopefully whoever told you that you should have done that clarified that little issue.

I don't like anything about the regulator or manifold location. That is uuuugly.

Although it is debatable about whether or not it is an issue, I think it is a bad idea to supply the manifold with 1/2" black iron and then pull a 3/4" line off it. Honestly, it shouldn't ever be an issue. Along the same line, most gas meters for 1/2lb systems have a 1" hookup...Even if there's a 2" or 3" gasline needed to supply the home's demand.
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Old 01-30-2009, 09:53 AM   #5
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Gasing a Tankless Water Heater


Quote:
It has been installed for a couple of weeks and don't know enough about diagnosing optimal vs. just "ok" performance.
Do you get enough hot water for your showers etc? If you do then I would say it is working fine.
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Old 01-30-2009, 12:45 PM   #6
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Gasing a Tankless Water Heater


beenthere,
so, are you indicating that a larger line be installed from the meter? or are you agreeing that the water heater line should come off of the incoming line before the regulator (which means a second regulator is employed at the water heater itself)? I thought they would have just tee'd the incoming line as it came into the house and ran 3/4" to the water heater and just couple the current supply line to the furnace but they said there wouldn't be enough volume to operate the water heater that way. Now, I don't see how tapping down the line at the furnace provided more volume?

Last edited by todolist; 01-30-2009 at 12:59 PM.
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Old 01-30-2009, 12:48 PM   #7
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bondo,
you suggesting that a larger line be brought in from the meter? things do seem to be working ok.

Last edited by todolist; 01-30-2009 at 12:55 PM.
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Old 01-30-2009, 12:54 PM   #8
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Gasing a Tankless Water Heater


thekctermite, they did use the existing line from the meter. not sure if that should have been changed. but i think what you are saying is that it should have been "tee'd" before the existing regulator to take 3/4" to water heater (use a second regulator at unit) and continue the 1/2" line to the existing regulator and on to the furnace as it was before the water install. i agree its not pretty but it does seem to be working.

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Old 01-30-2009, 01:05 PM   #9
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Gasing a Tankless Water Heater


Bondo, the 3/8" copper is more than likely not an issue at all. On a 1/2psi system it definately would be, but we're dealing with a medium pressure 2psi system that has drastically larger gas delivery. At 2psi, a 20' length (for example) of copper (from the meter to the regulator) can support 348,000btu/h's, compared to a 1/2psi system that would only deliver 38,000 btu/h's.


Todolist, no, I was referring to the piping on the appliance side of the regulator. I just would have gone with 3/4" instead of 1/2". I seriously doubt that it is a big deal at all.
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Old 01-30-2009, 02:47 PM   #10
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Gasing a Tankless Water Heater


They should have connected the manifold up near the gas meter.
Then ran a seperate gas line to each appliance, and used a regulator at each appliance.
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Old 01-30-2009, 02:48 PM   #11
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Gasing a Tankless Water Heater


thekctermite, water heater 199kbtu and 2-stage furnace high 80kin/74kout and low 56kin/52outbtu ............ is there somewhere that will help me figure gas line sizing for both units? meter to regulator is about 15' 3/8" copper and 25' of 3/4" from manifold to water heater and the rest is in the photos.

Last edited by todolist; 01-30-2009 at 05:33 PM.
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Old 01-30-2009, 02:55 PM   #12
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Gasing a Tankless Water Heater


thanks for the input beenthere. you should have beenthere when they installed it! if i have problems down the road, i think i'll have someone put the manifold or a different tee (including the line to water heater) before the existing regulator and put a separate regulator at the water heater. that ought to do it and seems easier than rerouting considering the lines are already running through the joists and converging there now.

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Old 01-30-2009, 10:08 PM   #13
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Gasing a Tankless Water Heater


Quote:
Originally Posted by beenthere View Post
They should have connected the manifold up near the gas meter.
Then ran a seperate gas line to each appliance, and used a regulator at each appliance.
That would certainly work, but is not necessarily a better way of doing things. Honestly, I've only seen that done a time or two, and have looked at hundreds of homes with 2psi systems. Here, 2psi systems are not the norm and are only put in when necessary or convenient. The manifold and regulator are usually set in a centralized location that allows shorter runs of pipe to each appliance. In my opinion, the fewer regulators the better.
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Old 01-30-2009, 10:12 PM   #14
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Gasing a Tankless Water Heater


Quote:
Originally Posted by todolist View Post
thekctermite, water heater 199kbtu and 2-stage furnace high 80kin/74kout and low 56kin/52outbtu ............ is there somewhere that will help me figure gas line sizing for both units? meter to regulator is about 15' 3/8" copper and 25' of 3/4" from manifold to water heater and the rest is in the photos.
The code has gasline sizing tables. Based on the 15' length to the regulator and the total btu/h's, I have no doubt that the 3/8" copper is adequate for your home's demand.

For sizing purposes, a system like yours is sized as two separate systems starting and stopping at the regulator.

The 3/4" pipe is good for 200,000btu/h's at 30', so at 25' you're definately good.

Stop worrying!
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Old 02-01-2009, 10:34 AM   #15
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Gasing a Tankless Water Heater


Done worrying! I'll leave it alone. Thanks for the input guys.

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