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LeighC 12-06-2012 08:19 PM

Brand New Concord Furnace Doesn't Work In Cold Weather
I purchased a 90% efficient condensating Concord furnace, model number 95G1UH090CP16 in mid-October of this year with a Honeywell programmable thermostat. When it was installed in October, the weather was mild (in the 50s) and the furnace worked great. However, now that it's December and has gotten quite cold in New England, the furnace is on the fritz despite being brand new. The plumber who installed it (and another guy from the same company) has been out to try to fix it, and cannot figure out what's wrong with it - an HVAC repair guy from a different company was out, and cannot figure out what's wrong with it. The plumber called Concord Tech Support, and they couldn't figure out what was wrong with it - but I haven't had heat for 2 weeks despite temps below freezing, and I have a 1 year old son, so I'm getting a little desperate here. Here's what I know:

- There is 18 feet of piping and 4 elbows (5 elbows allowed with up to 19 feet of piping, so we're below that)
- Everything is properly pitched toward the furnace
- The drain piping etc appears to be installed correctly, and drains into a condensate pump that appears to be functioning properly
- There are no clogs/debris in the intake or exhaust pipes. There is no soot/dirt clogging any parts, it's only been in use for a month and a half
- By all appearances, there is nothing wrong with this furnace except for the fact that it doesn't work

The symptoms:
- If the temps outside are mild, the furnace works fine and keeps my house at the set temperature with no issues. If it gets cold, the following happens:
- Fan turns on, burners ignite, everything works properly for anywhere from 30 secs-3 mins. Then everything shuts down, blower turns on. It doesn't get nearly warm enough to get the house up to temp, but everything turns on and appears to be running properly while it's running
- Sometimes a pressure switch error that indicates the pressure switch trips while the inducer is open (3 blinks) gets thrown. Other times, it's just a solid light, indicating no problem at all (even tho there clearly is one)
- There is water getting into the inducer fan. I do not know where it's coming from. According to the Concord tech support guys, it's not possible. He said the only reason for water in the inducer fan is that the furnace is double trapped (it's not - we did have the drain pipe in the hole of the condensate pump, but it has since been moved to make absolutely sure it's not touching the water when it rises)
- The furnace doesn't drain while it's running, but I believe it should... It drains after the burners go out and everything shuts down
- There is no lock out; if I set the thermostat high (in the mid-70s or 80s) the furnace will kick on and off every half hour or so, but it only runs for a little bit before going out. If I turn the temp down on the thermostat until the request for heat turns off and then turn it back up so the request for heat comes back, it turns the furnace on - I do not need to manually turn power on and off to the furnace, the thermostat does its job, but the furnace only runs for a little while each time
- It is not a thermostat issue, as jumping the wires doesn't solve the problem
- The pressure switch appears to be operating properly, as does the sail switch and the rest of the furnace. There's clearly a drainage issue due to the water in the inducer, but everything appears to be installed properly and the condensate pump is working - also, if it wasn't hooked up properly, it wouldn't work fine in warmer weather

I'm not even looking to DIY this, but I'm not sure what to do at this point - 2 plumbers, an HVAC guy, and the Concord tech support dudes are stumped, and I'm frickin freezing. I have a brand new furnace and no heat - the place I bought it from has a guy who's Concord certified, but he's on vacation for another week (of course). Does anyone maybe have ANY insight that I can pass along to the pros as to what could possibly be wrong with this furnace? Thanks in advance.

techpappy 12-06-2012 09:28 PM

what type of environment is the furnace located?..basement, heated space? attic..what temp is the furnace room/enclosure? Where does combustion air come from..inside or outside and could it be of high humidity?

Seems like a lot of elbows but, I don't have the install info..definitely trapping water in the ID fan ..must be a reason...anyone else out there who may be able to shed some light on this?

beenthere 12-07-2012 03:52 AM

Post pics of the furnace, trap, drain line, and of the flue pipe and its outside termination.

bandbsheetmetal 01-05-2013 06:41 PM

did you get it fixed? I have an HVAC shop in montana I also have 2 concord 92% and an armstrong 95% doing the same thing i'm gonna lose my business if i dont get this fixed.

carmon 01-05-2013 07:18 PM

loose your business over a couple of furnaces..... i sure hope not..... whats seems to be the problem.... there just furnaces let's fix them its not that hard..... give us more details ....... lots of smart tecs here.....:thumbsup:

bandbsheetmetal 01-05-2013 07:59 PM

please help
call for heat inducer kicks on and sometimes it fault code 3 preasure switch open with inducer on. the switch has two hoses one pulls -.5 in wc and the other pulls -2 in wc. the switch is rated to pull close at -.65 in wc
ive switched out boards and switches
tech support says there is something wrong with my vent or drain
one unit isnt on its own dedicated curict so they blame that the others are on there own curcut
one doesnt use long sweep 90's but it will flash the code sometimes with the vent pipes disconected
i just read the manul again and cant see that im doing anything wrong
i did see that the unit is to be tilted ever so slightly forward so i'll try that tomorrow
ive jumperd the r and w termal to cut out the t-stat wire and t-stat
one furnace i switched out and it stopped for about a year and now its doing it again
the distributor had me fill out a jobsite sheet with a ton of measurments and voltages and they said it all checks out
my other supplier said that above 4500 ft in alt i need to use a high alt switch that has a little less rating to close the switch its 2500 ft here so i dont think that applies
all these units are in retro fit change out not new construction
they are all direct vent
they are all upflow in basenents
i thinks they are all 70k btu units
one is a armstrong 95 and the other two are 92 concords
i stopped putting in the 92's after the second problem happened last year
the armstrong was the fist to have it happen???? it was dented a little bit when it got here like it had been dropped but i used it cus i'm so remote and i have to ship stuff in and he had no heat
i dont know what else to to i'm being threatend to be sued and this is a small town i can get a bad name here and i dont like not being able to help them

bandbsheetmetal 01-05-2013 08:11 PM

he manul :

carmon 01-05-2013 09:42 PM

pictures really help''''' I have installed hundreds of furnaces.... never have not been able to fix one...... they are easy/..... get yor meter out and fix it....

bandbsheetmetal 01-05-2013 10:00 PM

ive had my meter out for days and i'm out of anwsers

Marty S. 01-06-2013 10:16 AM

Give us some details of what your combustion analyzer readings are. Need 10 minutes worth with readings every 2 minutes. Pressure switch seeing constant vacuum or is the pressure fluctuating? Those two things will point if it's an inducer problem or water backing up in the secondary heat exchanger.

bandbsheetmetal 01-06-2013 11:38 PM

marty please help! this problem is right when it starts up before the gas valve opens

carmon 01-07-2013 12:32 AM

sounds like pressure switch..... is it making .... ventor motor starts ...makes pressure switch,,, then glow coil... then gas valve.... or is this thing a spark ignition.... whatever..... if its before gas valve opens measure the pressure the switch's are getting...

bandbsheetmetal 01-07-2013 11:42 AM

-.5 in wc on the positive side and -2in wc on the other side

jagans 01-07-2013 12:37 PM

1 Attachment(s)
Does the condensate arrangement on this unit make sense to you pros out there? Looks like a pipe dream to me. See attached.

jagans 01-07-2013 01:10 PM

1 Attachment(s)
I have a theory. I am not an HVAC tech, but understand air flow, being AF trained re aerodynamics etc. Bernoulli etc.

Is it possible that condensate water is running over to the right and covering the condensate drain on the secondary HE? Maybe the inducer fan is not creating enough of a draft to pull a solid column of water up that tube but it can pull a surface skim of water. Like a shop vac when you are trying to vac up water. You have to let air travel over the top within the tubing to draw up water, otherwise it will try to lift a solid column of water, and it cannot do it. Maybe if the furnace is tilted just slightly to the left, away from the drain on the secondary heat exchanger, it would solve the problem?

The design seems flawed to me, in that the condensate should not have to go uphill, but You all probably know better, being experts.

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