Cold in Chicago

I just bought a house with a Rheem forced-air gas furnace upstairs with an electronic pilot light and a manual thermostat. Here's the problem: For about 17 hours every day it works fine. Every night around bedtime it shuts down for several hours and won't restart. I've tried turning it off and on. It just comes one for a few minutes, blows cold air and shuts down. Can it be a bad thermostat if it works fine the rest of the day? I'm confused and need some help. I'd call a service technician, but he would come during the day, charge me a $100 service call, and tell me it works fine. Help?
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My house is like that too. I think during the day, people are walking around helping circulate the air and preventing the buildup of static temperature gradients.
At night when the air is still, the bedrooms get cold, but the thermostat (in the hallway) stays satisfied.
I don't have an answer.... That just seems to be the way it works. That being said, check to see if your thermostat has some sort of anticipator adjustment. It's supposed to prevent wide temperature swings.
Beachcomber
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Sounds like it's actually controlled by a programmable t-stat. (Does your manual t-stat actually control the temp setting at other times?)
Or it's haunted.
Sorry, but your limited understanding of the system, implied in your question, means that you need to call in someone who can answer your questions. Provide a full description and list of questions up front, or arrange to be there to ask personally.
And ... you would benefit significantly from a programmable t-stat, using setbacks (night and mid-day) as deep as possible. Small price differential from fixed-setting oldies.
J
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What make and model thermostat
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I don't know the brand, but its one of those brown dial thermostats. I've played with various settings on the heat anticipator with no results. The t-stat does control the heat and temperature most of the day. In the evening hours, temperature drops all the way to low 60s. Sorry J, but if it weren't for my limited understanding of the system I wouldn't need to ask for help.
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I'm going to guess that the anticipator is set for too short intervals. Of course, it could be other things causing the problems too. As most new furnaces turn the blower on immediately when the thermostat calls for heat, cold air will blow until the heat exchanger gets hot .... a bad idea, from a comfort standpoint, IMO. Usually there is a current rating on the gas valve or control system, which is the setting of the anticipator. You can go a bit "longer" or "shorter" than that setting, however, not too far. Too far towards the shorter, will probably cause problems as you describe. I usually start at the rated setting, and adjust from there a bit, as required. Of course, as some have said, a programmable unit is much better. The one I have, basically, does the anticipation function in the software (firmware), but I have seen it turn on and then off, prematurely, especially when there is aa outdoor temperature swing
dave wrote:

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Dave,
Competent expert who can see your system can help you understand how your system works; we, at a remove, cannot, except in broadest generalities.
Thermostat can only control temp of its location. Is it doing that? For a couple $, you can get various accurate thermometers from hvac-supply or big-box. The old Honeywell I replaced with programmable has a thermometer that's close up to about 67 deg F. Then it doesn't move until temp is above 75 deg F, whereupon it indicates 68 deg F. IOW, useless.
Other spaces, to be heated controllably, need to be in communication with system and t-stat. Meaning, for instance, if heated air is pumped to area of t-stat more so than to other areas, and those other areas are in poor communication, they will be cooler.
Also, discharges and returns must be designed for consistency from floor to floor, with heating and a/c. Sometimes kids like to play with registers, too.
In a different vein: When you "make" the t-stat, pull the outer cover so you can see the mercury switch. Do you see the mercury surge to cover the contacts? The burner should now light. Depending on the setting of the fan switch, when the heat exchanger warms up to fan-switch set-point, the fan will start. Later, t-stat will open, burner stop, furnace cool and fan to off. Easy enough to track this sequence. When you drop the setting so that the mercury surges the other way, do you see a small arc as the contacts open?
J
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This sounds like something I would intentionally do to save on heating costs. i.e. Program the thermostat to go down to about 60 in the late evenings.
Find out the brand and model number of the thermostat. And the brand and model number of the furnace. Next find the instruction manuals for these - perhaps on the internet. Or ask here. If you are brave, ask on alt.hvac, but you would need to give them brands and model numbers...
"dave" wrote in message

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Maybe beachcomber is right. Regardless, have you tried turning the setting up at night, to 75 or 80?. 85?
OR: They make little heaters, on timers, that go underneath the thermostat, as a way to have a setback effectt without changing the themostat. Maybe you could do the opposite. Take a bag of frozen vegetables and hold it around the thermostat until the air inside gets colder. Does the furnace go on then?
If not, I guess I would try to debug the system as if it were always broken. The first step in that is, I think, bypassing the thermostat by shorting two of the wires together, as if the thermostat was calling for heat. I don't know about colors though, which wires to short.. You can also find the same colors at the furnace.
Maybe at night it gets cold somewhere and a broken wire causes an open circuit, but in the day this doesn't happen. This doesn't sound likely but neither does your situation. Like I say, learn how to fix it in general, and do so at night.
(My mother had a Zenith tv that was good for more than a decade, but once it broke. It was a tube set. Everytime I visited from out of town, the tv worked so I couldn't fix it. But one time I came home without telling her, and I tricked the tv. Caught it not working. All it was was a loose pin clip for one of the pins on the tv tubes. Worked well for years after that.)

Hack into his sytem and change his clocks by 12 hours. Then he'll come at night..
Remove NOPSAM to email me. Please let me know if you have posted also.
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The thermostat is simply a switch; inside it is a bulb with some contacts and some mercury that rolls back and forth inside the bulb to make and break contact as the bimetallic spring that holds the bulb expands and contracts with the ambient temperature. One can remove the thermostat, twist its 24 volt red and white wires together to get heat without any control - just ON.
The furnace's gas valve is opened by power from the thermostat, the furnace lights and when the fire box is warm the blower for the ducts will start to distribute the heat. The fire is cut off when the thermostat switches to OFF and the furnace blower runs until the fire box cools down when it shuts off.
That's basically how it works.
You said the furnace was upstairs. Is there another furnace for downstairs? If so are there timers on either furnace?
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You have one of the strnagest problems I have seen posted on here. You dont by chance have one of those electrical services that was inteneded to turn an electric water heater on and off by the electric company. I have mostly only seen those used in rural areas, but anything is possible. Be sure you have 120VAC power to the furnace just in case someone wired to some special circuit like this, or even a light times installed into your system. Once you prove you have 120VAC going to the furnace, you need to take the thermostat off the wall and short across the wires. (I's just low voltage, and wont hurt you). If the furnace starts, you need a new thermostat. (or thermostat battery, although I have never seen a manual obe with batteries).
I'm assuming this is a house, not an apartment or condo, where something could be controlled by a neighbor thru mis-wiring it.
One other thing, are you POSITIVE thats not a setback (programmable) thermostat?
If this dont do it, you probably do have a ghost and need a priest !!!
Mark
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Thank you for all the advice. It is an old Honeywell manual thermostat. Indeed there is power to the furnace, with a switch box. The furnace was installed 1992. I have watched the burner sequence many times. The thermostat is indeed calling for heat as it should. The ignition is firing red hot, but it doesn't appear to be getting gas for those several hours. This is what made me think it was a gas pressure problem upstairs at peak hours (when people are at home in the evening), but that may be ignorance on my part. I have looked all over for the timing mechanism that could explain the problem but can't find it. There is no wiring that would explain it. I'm beginning to like the ghost explanation. Anyway, my wife is pulling her hair out. And you can imagine what no heat at bedtime is doing for the more personal aspects of my life. Argh.
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thermostat.
The
problem
timing
no
pulling
for
There should be a wiring diagram on the inside of unit, most likely on one of the panels...
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furnace
is
but
is
on
Not that it will help you, though. If the igniter is coming on it sounds like any pre ignition interlocks are OK. Can you hear the gas valve solenoid clicking? It should attempt to light a few times (with a delay between attempts) before it shuts off and resets the sequence.
Could be flaky ignition module or gas valve, would need to check voltage to solenoid when it's trying to light.....
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Yes and no. Most houses have their own pressure regulator, and meter.
HOWEVER, some older sections of Chicago have neighborhood pressure regulators, I remember the news stories when one failed, and all the gas appliances in that neighborhood shot out huge jets of flame. So check and see if you have a meter and regulator setup. If you don't have your own regulator, then call the gas company and report the problem, and see what they say, because then what you think may be true.
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I have no idea what I did, if anything. But it seems to working now, who knows. I will attribute it to alt.home.repair and all the great help. Until my ghosts return, thanks a lot.
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