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Old 11-07-2011, 01:36 AM   #16
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Is this old Furnace Able to be Serviced?


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Originally Posted by how View Post
To test for a possible exchanger crack and a possible safety concern for spillage being the reason the paint is falling off.

Turn up the thermostat, lay down on the floor and watch the flame from the burners, don't breath towards the burners or disturb the dust in the area. Wait until the blower comes on to see if the flames change with the
start up of the blower. Do this for 10 minutes because some cracks only open up after the exchanger fully heats up. Make sure that a heating outlet is not blowing directly towards the burner area which will mess up your results.

Do this test again but this time turn down the flames on the burners as low as you can without them going off. This is done with a carefull partial tuning down of the main gas cock to the right of your gas valve. This makes the flames very soft and more suseptable to the air disturbances that a cracked exchanger can cause. Once again you are watching for the flames to wave around when the fan starts.

Return the gas cock to the normally "on" position, close up all the windows and doors in your house, turn on your clothes dryer and use the smoke of an incense stick to make sure that the products of combustion are not coming out by the burners where the paint is now coming off. The smoke from the incense should be drawn into the furnace when the incense is brought in close between the inside and outside of the furnace just a 1/2 inch above the burners.

Let us know what you find.

Ps My other concern is that your present motor is dangerously ungrounded but it's easy to fix that by attaching a ground from the motor it to the furnace body.
I tried your testing and did not notice a difference in the flame when I turned on and off the blower but I'm not qualified to determine if what I was observing means that the heat exchanger is cracked or not. I didn't try the low gas test but I may give that one a try tomorrow. I need some one to help me because by the time I adjust the thermostat and run to the basement, it already starts up. It's just me and the wife at home now that the kids are off at college so I don't have as much help around the house for things like this.
You are right about the motor not being grounded. I have replaced about half of the 2/3 of the knob and tube wiring in my house but the receptacle that feeds the furnace does not have a ground. The gas pipe however is bonded to my water pipes which are bonded to my electrical panel and an 8' copper ground rod.

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Old 11-07-2011, 01:50 AM   #17
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Is this old Furnace Able to be Serviced?


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nice pix ...before i say push the fan temp up how HOT is the air coming out of the rgisters with a hand over them...i'll guess 87F and hw s the air coming out slightly... forceful...pick a word.you might want to bump that top dial up a bite like to 125F and if your short on air out of the register shut the furnace power OFFtake an allen key sitting in frontor kneeling and reaching in to the sheave/pully on the motor loosen the outer plate and ONE full turn away from were your sitting follow the allen key screw...and end up right back from where you started.. you just sped up the RPMs on the motor....this will bring in the sheave... speed up the motor and give you more air.tighten it down on the flat part of the threaded piece there....if the belt was a little loose this will actually tighten the belt up without adjusting the motor mounts....this is just info but easy to do but get back with quetions if you leary of doing this...but definitly bump that dial up a bit...it will give you hotter air and might solve the fan being on all the time.....with the unit off run your index finger inside th squirrel on the fan fins to see if you have any dirt dropping off them dust is OK but any dirt will cut down on the air being thrown up the duct to heat....do you have a good percentage of wood floors or carpet..pets dogs cats...just wondering always used 1" pleeted filters there.if you want to scent the house up for the hilidays a solid air freshener in the fan section will scent the entire house...thats freeeee
The air is warm when it comes out of thr registers. It feels nice. The dog likes it too. Sometimes, when the heat comes on, he runs over and sits in front of the register. I guess it wont hurt to try cranking up that dial to see if anything changes. How does changing that dial make for a hotter flame? Please explain.
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Old 11-07-2011, 06:37 AM   #18
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Is this old Furnace Able to be Serviced?


Soot is a sign of incomplete and bad combustion. Nat gas needs a precise air to gas mixture and draft to burn a nice clean blue flame. Soot is caused by a lack of oxygen AND or not enough draft thru the exchanger because the passages are blocked by soot. Proper combustion of gas gives you CO2 and water vapor and a small amount of sulphur. Lack of oxygen deletes one O molecule so you get CO instead of CO2. It is almost impossible to completely or properly clean a heat exchanger w/o physically removing it and taking it to the car wash and using high pressure water. Google natural draft gas burner for more info on how to burn gas properly. Or borrow the Fundamentals of Gas Utilization from the library. Rollout means exactly what it says.
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Old 11-07-2011, 11:15 AM   #19
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Is this old Furnace Able to be Serviced?


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Soot is a sign of incomplete and bad combustion. Nat gas needs a precise air to gas mixture and draft to burn a nice clean blue flame. Soot is caused by a lack of oxygen AND or not enough draft thru the exchanger because the passages are blocked by soot. Proper combustion of gas gives you CO2 and water vapor and a small amount of sulphur. Lack of oxygen deletes one O molecule so you get CO instead of CO2. It is almost impossible to completely or properly clean a heat exchanger w/o physically removing it and taking it to the car wash and using high pressure water. Google natural draft gas burner for more info on how to burn gas properly. Or borrow the Fundamentals of Gas Utilization from the library. Rollout means exactly what it says.
Thanks for the info. I appreciate your concern and sound advice. I just ordered a commercial CO monitor and it should be delivered to my shop by Wednesday. I'll test measure the concentration of CO at all locations and post the results for any other forum members who maybe concerned or are in a similar situation. In addition, I also order a 50ppm balanced with air calibration gas mixture so I will not test my existing $50 Home Depot CO monitor vs. my new $500 electrochemical commercial monitor and see if they both respond upon exposure to 50PPM CO. 50PPM is the Permissible Exposure Limit (PEL) of CO and 1200PPM is the immediately dangerous to life and health (IDLH) concentration for CO. Hopefully, the concentration that I measure will be less than both.
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Old 11-07-2011, 03:48 PM   #20
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Is this old Furnace Able to be Serviced?


maximum permissible concentrations per hour of CO for humans and the cumulative effects.

http://www.carbon-monoxide-poisoning...co-levels.html

http://www.epa.gov/iaq/co.html

http://www.osha.gov/SLTC/healthguide...cognition.html
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Old 11-07-2011, 10:54 PM   #21
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Is this old Furnace Able to be Serviced?


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maximum permissible concentrations per hour of CO for humans and the cumulative effects.

http://www.carbon-monoxide-poisoning...co-levels.html

http://www.epa.gov/iaq/co.html

http://www.osha.gov/SLTC/healthguide...cognition.html
Thanks for the additional information on carbon monoxide exposure limits and the cumulative effects. I usually use the OSHA PEL of 50 PPM as my alarm limit but if I'm even close to measuring that concentration in my home, then there is a serious problem that will need to be addressed immediately. I can hardly wait for my new monitor to arrive so that I can measure the concentrations with an accurately calibrated instrument.
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Old 11-08-2011, 06:47 AM   #22
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Is this old Furnace Able to be Serviced?


check it randomly near the furnace several times a week during one or two months( with it fired up obviously). You may lose the draft in your chimney or have a weaker draft on non windy days so checking it several times to get a good representative sample is required.
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Old 11-08-2011, 09:01 AM   #23
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Is this old Furnace Able to be Serviced?


200 years from now they are going to think we were nuts installing these potentially deadly heating contraptions in our houses
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Old 11-08-2011, 09:37 AM   #24
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Is this old Furnace Able to be Serviced?


adjusting the discharge air temp...as you make it higher on the setting the mercury bulb is on a metal pigtail sticking into the furnace between the chambers...as it heats up the metal expands and you get a higher temp.if your happy with that at 87F range leave it....later models run 150F and the fan comes on...i was just seeing about that fan running all the time..that soot on the front is from the heat Exchanger maybe carbonized with soot... have somebody brush up into it...during a maint.visit.the heating cycle on a unit that old is STAT calls .."standing pilot" main burner comes on....heat exchanger heats up and that controller reacts to the heat turns the fan on.....place heats up...stat satisfies...main gas off...fan removes balance of heat into the space heate exchanger cools off and the controller reacts below setting and fan goes off till next cycle...
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Old 11-08-2011, 04:56 PM   #25
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Is this old Furnace Able to be Serviced?


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200 years from now they are going to think we were nuts installing these potentially deadly heating contraptions in our houses
Yes for sure. It's like those old Victorian Homes that have gas wall lamps. Those things freak me out.
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Old 11-08-2011, 05:12 PM   #26
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Is this old Furnace Able to be Serviced?


i first off want to admit that i did not read every post post in this thread, but the simple answer to the posters question is yes of course any furnace can be repaired. In this case it is not advisable, due the the obvious signs of flame roll out in the burner area,this is a sure sign of a much more serious and potentially deadly condition that exist. Replace this unit, do not repair and also take it out of service right away.
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Old 11-08-2011, 05:29 PM   #27
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Is this old Furnace Able to be Serviced?


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Originally Posted by biggles View Post
adjusting the discharge air temp...as you make it higher on the setting the mercury bulb is on a metal pigtail sticking into the furnace between the chambers...as it heats up the metal expands and you get a higher temp.if your happy with that at 87F range leave it....later models run 150F and the fan comes on...i was just seeing about that fan running all the time..that soot on the front is from the heat Exchanger maybe carbonized with soot... have somebody brush up into it...during a maint.visit.the heating cycle on a unit that old is STAT calls .."standing pilot" main burner comes on....heat exchanger heats up and that controller reacts to the heat turns the fan on.....place heats up...stat satisfies...main gas off...fan removes balance of heat into the space heate exchanger cools off and the controller reacts below setting and fan goes off till next cycle...
Thanks for the reply biggles but I'm new to furnace work and your slang and incomplete sentences is very difficult for me to follow. I do appreciate you taking the time to write me back and the info you presented sounds useful if I could decipher your "lingo".
I just really want know why my fan runs 24 x 7 whether the not the burner is on or off. It sounds like it might have something to do with that dial. Are you saying that if I raise the setting from 87 to 150, my fan will have the ability to turn off sometimes?
I'll probably wait for my CO monitor to arrive before making any adjustments but I'm still trying to understand why the fan is always running.
If anyone knows a good old timer HVAC man in the South SF Bay Area who can help me out, I'm all ears. Thx, VC
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Old 11-08-2011, 05:43 PM   #28
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Is this old Furnace Able to be Serviced?


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Originally Posted by harleyrider View Post
i first off want to admit that i did not read every post post in this thread, but the simple answer to the posters question is yes of course any furnace can be repaired. In this case it is not advisable, due the the obvious signs of flame roll out in the burner area,this is a sure sign of a much more serious and potentially deadly condition that exist. Replace this unit, do not repair and also take it out of service right away.
Thanks for the advice. Since you have not read the threads, I will fill you in on what's going on.
I have ordered a commercial grade CO monitor that is due for delivery tomorrow. The results of my tests and the measured CO concentration will determine whether or not I take this heater out of service or not. If I don't measure, CO flowing into my home, is there still any other reason to take this furnace out of service?
Everyone keeps mentioning flame roll out. I watch the unit when it starts up and when it burns and I don't see any flames rolling out. There might be a little flash when the flames ignite but its not like the fire is burning outside of the furnace.
Does flame roll out mean that flame are burning outside of the chamber?

Thx, VC
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Old 11-08-2011, 06:08 PM   #29
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Is this old Furnace Able to be Serviced?


The fumes are spilling out the front of the furnace and you cannot see or smell them. At that age the heat ex can be partially plugged with normal rust and has some soot from bad combustion. You may also have a draft problem with your chimney and not enough draft thru the furnace caused by the plugging up heat exchanger. Visual signs like that are HUGE red flags and it depends on the homeowner whether he wants to see them or not. Natural gas natural draft furnaces like yours are not on/off logical devices where they can be considered safe or not. Experienced Pros have seen that those units and have done CO poisoning calls and know what units generate those calls.

A properly burning and drafting furnace can go 30-40 yrs where I am and have NO sign of spilling or charring.
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Last edited by yuri; 11-08-2011 at 06:11 PM.
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Old 11-08-2011, 06:50 PM   #30
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Is this old Furnace Able to be Serviced?


There's also a 200ppm limit of CO in the flue gas even if it's not dumping into the house. Soot in the exchanger results in CO levels many times that. Perhaps your new meter can test that too. It might ruin it in seconds though so read the directions.

The reason most have not got into the fan issue is we,as techs in the field, make sure the furnace is safe before moving on to any other issues. The same concern is carried over with our advice on this forum. Step one is ALWAYS peoples safety.

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Last edited by Marty S.; 11-08-2011 at 07:18 PM. Reason: added info
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