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Old 02-02-2020, 07:20 AM   #16
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Re: Bryant plus 80t furnace power issue?


Where I am all furnaces use 15 amp breakers and so do circuits for living rooms.

Only stoves, dryers, elec baseboard heaters and AC's use 20 or 30 ampers.

Check the wiring in the main panel including the neutrals to make sure all are tight.

Check the wiring to the furnace and make sure it is not aluminum wiring. If it is check all connections to make sure they are very tight. Aluminum is soft and notorious for loose corroded burning connections.
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Old 02-04-2020, 04:39 PM   #17
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Where I am all furnaces use 15 amp breakers and so do circuits for living rooms.

Only stoves, dryers, elec baseboard heaters and AC's use 20 or 30 ampers.

Check the wiring in the main panel including the neutrals to make sure all are tight.

Check the wiring to the furnace and make sure it is not aluminum wiring. If it is check all connections to make sure they are very tight. Aluminum is soft and notorious for loose corroded burning connections.
So today I messed around with the furnace in an attempt to try and figure it out and I think I'm on to somthing. I ran the furnace from 55 degrees to 70 degrees and the furnace short cycled and cut off at 67 degrees followed with the blinking code 33, by the time the furnace had a chance to come back on I removed the air filter and then let the furnace continue heating the house up so I went ahead and turned it up to 75 degrees and it gradually heated the place up with no problems at all. So question that's on my mind is the furnace blower motor becoming so weak that it's no longer able to suck air through a merv 5 air filter anymore?
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Old 02-04-2020, 05:13 PM   #18
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Re: Bryant plus 80t furnace power issue?


Is the blower wheel clean?

Do you have a/c? Coils can get dirty.

Capacitors can get weak and reduce motor rpms.

Gas valve regulators can drift causing over-firing or under-firing -> meter can be clocked to verify proper btu input.

Have you actually measured the temp rise across the furnace? - i think i mentioned it early in this thread.
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Old 02-04-2020, 06:13 PM   #19
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Is the blower wheel clean?

Do you have a/c? Coils can get dirty.

Capacitors can get weak and reduce motor rpms.

Gas valve regulators can drift causing over-firing or under-firing -> meter can be clocked to verify proper btu input.

Have you actually measured the temp rise across the furnace? - i think i mentioned it early in this thread.
I blew dust out of the blower wheel when I removed it last week and it wasn't to dirty. I do have A/C coils but isn't that irrelevant to the actual furnace operation? What kind of tool can i buy to measure temp rise?
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Old 02-04-2020, 06:26 PM   #20
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Re: Bryant plus 80t furnace power issue?


You need a digital thermometer with a stem you can insert into the duct.

It gets put into the return and into the supply, but can't be in line of sight with the heat exchanger.

All the air that the furnace moves goes through the indoor coil - if it's plugged up furnace can overheat.

If the capacitor is weak, the motor will take longer than normal to get up to speed.
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Old 02-04-2020, 07:43 PM   #21
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Originally Posted by user_12345a View Post
You need a digital thermometer with a stem you can insert into the duct.

It gets put into the return and into the supply, but can't be in line of sight with the heat exchanger.

All the air that the furnace moves goes through the indoor coil - if it's plugged up furnace can overheat.

If the capacitor is weak, the motor will take longer than normal to get up to speed.
Just to be clear were talking about a digital thermometer like a person would use right?

Tomorrow I will check that evaporator coil out and see if it has any dirt plugging it.

I may pick a thermometer up and get some readings on it. What temp am I looking for on the output and intake?
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Old 02-04-2020, 07:47 PM   #22
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Re: Bryant plus 80t furnace power issue?


the furnace label should state the temperature rise ranges for low and high heat respectively. temp rise is difference between the supply and return temp.

Generally 40 to 50F difference is good and if it's 60F+, there's an overheating condition.

Granted some modern furnaces are rated up to 70F rise but they shouldn't really be running that hot.

You may find it's only cycling on limit on high fire. Have you changed the way you operate it - large t-stat setbacks, different stat?

It may have been cycling on limit since day 1 but u never noticed due to cycles not being long enough to see a lockout.
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Last edited by user_12345a; 02-04-2020 at 07:49 PM.
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Old 02-04-2020, 08:01 PM   #23
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Originally Posted by user_12345a View Post
the furnace label should state the temperature rise ranges for low and high heat respectively. temp rise is difference between the supply and return temp.

Generally 240 to 50F difference is good and if it's 60F+, there's an overheating condition.

Granted some modern furnaces are rated up to 70F rise but they shouldn't really be running that hot.

You may find it's only cycling on limit on high fire. Have you changed the way you operate it - large t-stat setbacks, different stat?

It may have been cycling on limit since day 1 but u never noticed due to cycles not being long enough to see a lockout.
I haven't really did anything to this furnace in the 4 years that I have owned my property besides change the filter and keep the dust blowed out of it. I remember last summer the blower motor wouldn't turn it's self off when using the A/c and I had to turn the whole system off to get it to stop.
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Old 02-04-2020, 08:55 PM   #24
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Re: Bryant plus 80t furnace power issue?


^Was that resolved?
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Old 02-05-2020, 06:28 AM   #25
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^Was that resolved?
I guess it was because it never has gave me any other issues
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Old 02-05-2020, 11:55 AM   #26
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Quote:
Originally Posted by user_12345a View Post
the furnace label should state the temperature rise ranges for low and high heat respectively. temp rise is difference between the supply and return temp.

Generally 40 to 50F difference is good and if it's 60F+, there's an overheating condition.

Granted some modern furnaces are rated up to 70F rise but they shouldn't really be running that hot.

You may find it's only cycling on limit on high fire. Have you changed the way you operate it - large t-stat setbacks, different stat?

It may have been cycling on limit since day 1 but u never noticed due to cycles not being long enough to see a lockout.
This morning I test all of the vents and they all put out 110+ degrees before the thermometer starts displaying HI. The air intake would not display anything on the thermometer because it was to cool so it displayed LO. I'm about to try to get a look at the evap coil
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Old 02-05-2020, 12:04 PM   #27
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Quote:
Originally Posted by user_12345a View Post
the furnace label should state the temperature rise ranges for low and high heat respectively. temp rise is difference between the supply and return temp.

Generally 40 to 50F difference is good and if it's 60F+, there's an overheating condition.

Granted some modern furnaces are rated up to 70F rise but they shouldn't really be running that hot.

You may find it's only cycling on limit on high fire. Have you changed the way you operate it - large t-stat setbacks, different stat?

It may have been cycling on limit since day 1 but u never noticed due to cycles not being long enough to see a lockout.
This morning I test all of the vents and they all put out 110+ degrees before the thermometer starts displaying HI. The air intake would not display anything on the thermometer because it was to cool so it displayed LO. I'm about to try to get a look at the evap coil
These readings were with the air filter out. I heated the house from 56 degrees all the way up to 65 degrees with no problem
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Old 02-05-2020, 12:38 PM   #28
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Re: Bryant plus 80t furnace power issue?


You need to check near the furnace, not at the vents.

You need a proper thermometer that can read well above 110F -> cooking/lab.



It gets inserted into the supply duct near the furnace, but not in line of site of the heat exchanger.

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I am not in the business of any trade I give advice on. I have non-professional hvac experience + good knowledge of theory. Attempt repairs at your own risk. Never jump out safeties - especially pressure switches - on a furnace for testing with fuel supply on; use a meter. Do not troubleshoot with live line voltage present unless there's no alternative.
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Old 02-05-2020, 08:28 PM   #29
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Quote:
Originally Posted by user_12345a View Post
You need to check near the furnace, not at the vents.

You need a proper thermometer that can read well above 110F -> cooking/lab.



It gets inserted into the supply duct near the furnace, but not in line of site of the heat exchanger.

I will buy a better thermometer and test tomorrow. I looked at the top part of the evap coil and it was honestly pretty clean and when I turned the fan on the air was moving through the coil fins really well and it didn't seem air restricted at all.
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Old 02-05-2020, 08:46 PM   #30
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Re: Bryant plus 80t furnace power issue?


It's the underside/inlet of the coil that gets dirty, the top/exit side can look perfectly clean.

You have to test the rise on both stages - if you have nothing connected to W2 it will take 16 minutes after a hard reset for high to come on, from there could take another 5 to 10 minutes to stablize.
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