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Billy
Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 19712
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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We have a Carrier 376BAW060115 model furnace. We have not used

Resolved Question:

We have a Carrier 376BAW060115 model furnace. We have not used it for few years. A local technician installed a new control board (ICM275 and a digital thermostat on the wall). It worked well for a week and then stopped (nothing happens, no blower, no pilot, nothing). The technician came did something (did not tell us what) and it worked for another week and then stopped. He came again, did something, it worked for another week and then stopped. I opened the controller cover and saw that the red blinks (very short and faint pulses of light) but nothing else happens. I am moderately technical and have a volt/ohm meter if you need more info. The technician said that the unit is too big for the house and that we need to get a new and smaller unit. He also mentioned that he disabled some of the flames to reduce the heating power (?). I would like to understand what is wrong and to fix it. Please advise.
Submitted: 1 year ago.
Category: HVAC
Expert:  Billy replied 1 year ago.
Hello,

this can go quickly with the volt meter.

Can you also tell me if the blinks on circuit board are continuous...or are they flashing a pattern?

The Carrier/Bryant flash a 2 digit code in the form of a set of short blinks followed by a set of fast blinks.


Customer: replied 1 year ago.

Continuous short blinks, one every second. The ICM275 manual says no error flash codes for this controller http://www.icmcontrols.com/ProdImages/ig_LIAF083-1.pdf


 

Expert:  Billy replied 1 year ago.
The unit still maintains a solid for correct operation though.

Can you tell me what voltage you have on the circuit boar between terminals R and C where the thermostat wires attach?

Expert:  Billy replied 1 year ago.
I see the 275 blinks just to prove 24v to secondary terminals from transformer.

R to C will tell us if that 24v is getting out of board past safeties

Customer: replied 1 year ago.

I see 27.4 VAC between R and C

Expert:  Billy replied 1 year ago.
Thank you.

Now what function would you like right now and we will bypass to that function as a test

Customer: replied 1 year ago.

The function I want is for the heating to work. Does this answer your question?

Expert:  Billy replied 1 year ago.
Yes,

now jump R to W and tell me result.

The jumper must be held in place .

Customer: replied 1 year ago.

Jumped R to W, plugged into power, observed for 5 minutes. Led still blinks but nothing else happens.

Expert:  Billy replied 1 year ago.


Is this unit installed as downflow?

Billy

Expert:  Billy replied 1 year ago.
I would like to check the safetys also, do you want a parts placement pic?

Customer: replied 1 year ago.

I am not familiar with the up/downflow terms. Here are two pictures of the unit. Hopefully it will give you the information you need


 


http://imgur.com/sQSaeSY,7BAifzm#0


http://imgur.com/sQSaeSY,7BAifzm#1

Customer: replied 1 year ago.

Yes, part placement will be useful. I am not familier with HVAC systems.

Expert:  Billy replied 1 year ago.

Thank you.

So when R is shorted to W...the exhaust fan (the fan above burners) does not start?

See page 3 HERE then locate switch number 1 and 11. Press the center of those and tell me if one clicks.

Billy

Customer: replied 1 year ago.

Bingo! The switch on top of the main blower clicked and now the burners start (the unit looks different than the document you sent me, one switch is up above the main blower and one at the center near the small fan).


 


What does it mean, did it get over heated? Should we block even more burners?

Expert:  Billy replied 1 year ago.
Ok,

usually this trips if the unit is turned off during a heat cycle. The heat rises and trips the switch.

Also-

Dirty filter
Dirty ac coil...the front cover of the very bottom cabinet comes off...look to see if the coil is plugged with dust.

Also we can speed up the blower if needed.

When the burners light...do they all light is one plugged off?

Customer: replied 1 year ago.

Two of the 6 burners were disabled by the tecnician. You can see the pictures here (notice the aluminum foil on the left burner)


 


http://imgur.com/ijNjMJp,3lFAUKp#0


http://imgur.com/ijNjMJp,3lFAUKp#1


 


I just looked at the coil, it is very clean. Probably as part of the service we had.



What would you recommend us to do to avoid repeating this problem?


How do we speed up the fan?

Customer: replied 1 year ago.

Should we replace that manual-reset switch in case it became too sensitive?

Expert:  Billy replied 1 year ago.
Wow,

No offense but that is not a good or safe way to block an orifice. It must be plugged with a blank. That is actually dangerous the way it is done.

I would find little faith in a tech that downfired a furnace like that.

It appears you have plenty duct work for return.
Of course we cannot see what the supply duct is....when cooling does the unit blow air out the registers nicely?

Then we will move forward
Customer: replied 1 year ago.

I just turn the cooling and we have nice flow of air throughout the house. Does this answer your question?


 


Closing the two burners did not solved the problem so possibly we did not need them in the first place (this is an old system and we never had this blower shutting off problem before).

Expert:  Billy replied 1 year ago.
Ok,

On the circuit board....there is a terminal marke HI and a terminal marked LO. There are wires from the blower motor attached to these.

They can you tell me what color wire is on LO?

And also you are correct...all this could be simply caused by a weak limit switch.

Customer: replied 1 year ago.

LO = Red


HI = Black

Expert:  Billy replied 1 year ago.
Ok,

they left your heat on the slowest speed possible which is strange if you are running hot. The very first thing a tech does is speed up the blower.

Now...do you have a unused blue and/or yellow wire from the blower motor?

Customer: replied 1 year ago.

Yes and no. The motor has 5 wires going out of it. 3 of them are going to the controller


 


http://imgur.com/OFrLLVf,zhkNrUO


 


The red and black are connected to the controller here


 


http://imgur.com/OFrLLVf,zhkNrUO#1


 


 


 

Expert:  Billy replied 1 year ago.
I humbly stand corrected.

The red wire from board is plugged into the yellow which is the highest available short of black. The black wire is for cooling and is the highest speed. The yellow is next highest.

There is a test we can do called a temp rise test if you have a thermometer. Then we can tell if the furnace is actually running as designed or if the switch is bad...

There is a label in the unit with the model, volts etc....there is a line that reads Temp Rise....and then a range..like 30-55. If you have a thermometer and can get me that Temp Rise rating we can do a final test.



Customer: replied 1 year ago.

Here is the label


 


http://imgur.com/HjFa5jr


 


If I understand it correctly the temp rise is 45-75 degrees (Celsius?)


 


I have this thermometer


 


http://www.fluke.com/fluke/usen/Electrical-Test-Tools/Thermometers/Fluke-62.htm?PID=56096


 


It's the IR type. If it's not good, I can go and grab something from a store.

Expert:  Billy replied 1 year ago.
Thank you....you are on the ball!

We want to take the return air temp (while the furnace is running)...and then the temp coming out of the furnace. (as close to the furnace as possible or at the ac coil)

The temp rise is the difference between the 2 readings.

Customer: replied 1 year ago.

Here are the readings in Fahrenheit


 


1. Duct above the unit: 95


2. AC coil below: 182


3. Air vent at nearest room 130


4. Room temperature before the experiment: 80


5. Outside temperature: 92


 


If I undersand correctly the rise is 182-95 = 87F. This is on the high side and only with 4 out of 6 burners.


 


The entire house (two floors, total of 2500 sqft) got fast very fast so the ducting is good?


 


 


 


 


 

Expert:  Billy replied 1 year ago.
Is the return air duct really 95?

Normally we have 70ish return air.....
Customer: replied 1 year ago.

Yes, I measured 95 at the big metal plate above the cabinet http://imgur.com/wV3WQ2v,89upcTq#1 (I fully closed the cabinet before doing the measurements)


 


I tried to stay away from the chimney round pipe.


 


The temperature in the house was 80 before I turned the heating on

Expert:  Billy replied 1 year ago.

Ok lets go with a return air of 80 since that was room temp.

I would indeed expect the switch to trip occasionally. Thus I do not feel the switch is bad.

BUT....has anyone discussed whether the blower motor is actually running at the correct rpm? Are the fins clean in the squirrel cage?

Customer: replied 1 year ago.

1. Motor RPM never mentioned. Is there a way to measure? What the RPM should be?


 


2. Will it help to close more burners or partially close the gas valve that lead to the furnace help?


 


3. I am surprise why the manual reset switch near the blower trips. This is before the furnace right? If so it see mainly the incoming air temperature?


 


Some short circuit in the ducts where hot air is fed back to the intake is out of question, right?


 


 

Customer: replied 1 year ago.

Oops, I forgot to mention. I touched blindly the blower blades on both sides and they felt clean.

Expert:  Billy replied 1 year ago.
Nothing is impossible...I have seen incorrect gas pressure, return air registers carpeted over, return air registers never cut in...supply runs off return...

I am very surprised that this unit with 2 burners capped off still runs hot with the yellow blower wire hooked up.

The way I see it....you either have duct issues or a blower motor or dual blower wheel. not moving air as it should. The yellow wire on heat should more than eneough, especially with 2 burners capped.
And I am not sure you have had good trubleshooting on site.

But I can tell you your first issue was tripped limit and given the readings it is indeed tripping on limit.I would turn the blower delay all the way to the right for a longer cool down, and I would have the burners properly capped with plugs

Customer: replied 1 year ago.

Hi Billy, one more question if I may, you mention blank plugs, any idea where I can find them or what are good names for searching them on Google?

Expert:  Billy replied 1 year ago.
A home remedy you can do is to remove the orifices you want capped and fill the orifice with JB weld or another epoxy type agent.

Then write on that burner with marker that is capped off.

Billy

Billy, HVAC Technician
Category: HVAC
Satisfied Customers: 19712
Experience: Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
Billy and 7 other HVAC Specialists are ready to help you
Customer: replied 1 year ago.

Thanks a lot for your patient and help. It's the first time I am using just answer and it exceeded my expectations. I am closing this incident.

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