Carrier Rooftop Ignition Faults

[brentstex]

We monitor and control several Carrier 48TJD008-14 with a DDC system and have noticed several lockouts recently. The heating stage 1 signal has been present for days but the supply air does not rise. Turning off the stage 1 heat signal and then restoring it seems to reset the unit. This seems to be a soft fault that can be reset with out resetting the power.

We won't reset them in the future so that we can have a tech check for fault codes, but until then. Are there any faults that can be reset in this manner?

The units were manufactured around Jan 2000, and the ignition control board says Automatic Ignition Systems H33WP002A.

[timebuilder]

Yes. When you remove the call, you reset the board.

A ten year old carrier probably has a bad HX, leading to a rollout switch actuation by flame rollout.

Other problems typical for the unit include failure of the rollout switch itself, that when it has been actuated a few times, it never fully recovers the ability to close its contacts fully. It is typically not replaced when the HX is replaced, and it should be. The board itself can develop an undifferentiated "internal fault" and it can also show a rollout code when the switch is fine and there is no flame rollout.

Get your tech out there.

Get your post count up and apply for pro membership for more specific details in the Pro Technical Forum.

[Dallas Duster]

Are these zoned systems? Could just be the wind playing tricks on you. Most alarms can be reset in the manner you are doing, if it's something major it's just gonna trip out again. I always like a 3 strikes and your out policy myself.

[yellowirenut]

I thought most roll outs must be manually reset..he is resting in a soft manner.
i say we cant see from here to judge...it could be a dirty flame sensor or a dirty initiator..wasp nest in draft inducer..etc etc

[timebuilder]

I thought most roll outs must be manually reset..he is resting in a soft manner.
i say we cant see from here to judge...it could be a dirty flame sensor or a dirty initiator..wasp nest in draft inducer..etc etc

The limit in the blower compartment has a manual reset. The rollout does not.

[yellowirenut]

just looked in the manual..u are correct. I still say no one can say with certainty what it is.

[timebuilder]

just looked in the manual..u are correct. I still say no one can say with certainty what it is.

That's right. Only perhaps 90% certainty.








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[timebuilder]

Oh, and strangely enough, this is the one design wherein I have never found wasp nests.

Those little suckers sure do like the Lennox units, though.

[brentstex]

The customer's HVAC tech thinks that all faults have to be reset by a hard reset, but our experience shows that some heating faults must be soft resettable. The documentation that comes with the unit doesn't indicate which. I wondered if there may be other documentation you guys may now of. The manual we have is a catalog # 534-725

Thanks

[DPinst]

It is scary that a fault such as a roll out switch can be reset with out a visual inspection.As was stated before these heat exchangers are famous for rotting out.
You did not say whether the lock-outs are all on one machine?
I have even see wasps and flies nest in the regulator vent line (when the screen has rotted out) and cause problems with the heating side.

[timebuilder]

The customer's HVAC tech thinks that all faults have to be reset by a hard reset, but our experience shows that some heating faults must be soft resettable. The documentation that comes with the unit doesn't indicate which. I wondered if there may be other documentation you guys may now of. The manual we have is a catalog # 534-725

Thanks

As I said, the rollout switch normally closes when allowed to cool, unless it has been opened too many times, and can no longer close. It must be closed in order for the control board to initiate heat.

Your tech may be thinking of another brand, one of which I can say definitely must have its rollout switch reset by hand.

Carrier is not such a brand.

There are no lockout codes that cannot be reset by removing the call or the unit power. If a code exists because of a hard fault like an open rollout, the fault will lockout the board immediately when the call is made. If, however, the lockout is due to an "internal error," the board may work for a time, and then the code is set once again, and the unit locks out until it is again reset.

There is a panel in the control section with a label that lists the codes. If rollout is set, check the resistance of the rollout and the HX for holes.

[brentstex]

We will check the fault codes the next time it happens.

Thanks for the replies

[yellowirenut]

hmm..i am thinking yes carrier does have the manual reset ones...they are much older units..3-5 ton range. Have that wire that wraps around the burners then back to what looks like a black boob..u press the nipple to reset

[timebuilder]

hmm..i am thinking yes carrier does have the manual reset ones...they are much older units..3-5 ton range. Have that wire that wraps around the burners then back to what looks like a black boob..u press the nipple to reset

The new ones still have that boob, it's in the blower section screwed into the fan housing at about 2:00 o'clock. I see it on units with straight cool and the electric heat packages.

[Dallas Duster]

The limit in the blower compartment has a manual reset. The rollout does not.

I know electric heating unit`s have a manual reset at the top of the blower.On the gas heating you might want to double check the manual reset high limit on the 8 and up unit`s TJ series. When even the rollout is auto reset. When you jump up to a twinned heating section like in the E,F,A,and Z series the roll-out switches are manual reset. But on those larger series the limits are auto reset.

[timebuilder]

I know electric heating unit`s have a manual reset at the top of the blower.On the gas heating you might want to double check the manual reset high limit on the 8 and up unit`s TM series. When even the rollout is auto reset. When you jump up to a twinned heating section like in the E,F,A,and Z series the roll-out switches are manual reset. But on those larger series the limits are auto reset.

I wanted to keep this focused on units of that size. I think his tech must be thinking of rollouts of another brand.

[Dallas Duster]

I know electric heating unit`s have a manual reset at the top of the blower.On the gas heating you might want to double check the manual reset high limit on the 8 and up unit`s TJ series. When even the rollout is auto reset. When you jump up to a twinned heating section like in the E,F,A,and Z series the roll-out switches are manual reset. But on those larger series the limits are auto reset.

There you go I fixed it.

[jayhawker]

Some of those units had a board in them that was effected by RF noise from an outside source. The local Carrier distributor can tell you what to look for on the board to tell if it is one that is effected by RF noise. Had a unit thta was located close to a police radio transmitter tower and it would lock out randomly all the time until the board was changed to an updated version that addressed this problem and it hasn't happened since.