Reznor packaged unit blower motor problem:

[Anvanho]

Hi

We have several Reznor outdoor packaged furnace units; model types RPBL; on our commercial building.

One (of the three units) has just developed this malfunction:

When the thermostat is set to “heat” and fan to “auto”, the blower motor (A.O. Smith; 3Ø) runs only for about a minute, then shuts down … only to restart after a 30-45 second delay … behavior continues like this.

When the thermostat is set to “heat” and fan to “on”, the blower motor will then run steadily without shutting down … unit heats as conditions at the thermostat dictate.

I cannot find any unusually heavy amperage draw on any phase at any point in the run-shutdown-run sequence.

Heating does not kill when motor shuts down … not a heating issue …

Some problem in the fan circuit during heat “on” fan “auto” cycle.

Thermostat was just replaced; that didn’t help.

Thanks greatly for any suggestions.

[dandyme]

:gah::callpro:


go ahead and call your tech, he'll know what's got to be done and how to properly do it

[929rc51]

Who changed out the stat you or your tech? I would be looking at wiring between the stat and unit. Other thing is if the unit has an older fan limit switch it could be set wrong/faulty.

[Anvanho]

Thanks for those replies; I changed out the thermostat; have done before in this (and other) buildings; problem I described existed before I did anything.

[acwizard]

The Reznor unit can not be wired with a typical thermostat, it is designed to have fan run during building occupied hours and heat to cycle with temperature controller. I am very familiar with this unit. Our company does startup and some warranty work for Reznor units. What is the wiring diagram number on the nameplate or the complete model number of the unit.

[Anvanho]

Model# HRPB125-8-S-MV
Wiring Diagram 224513
Manufactured July 2004

I see now on a more detailed service manual (Reznor website online) that they recommend a different fan control [kit] depending on if it was made before/after 2004;

[acwizard]

Model# HRPB125-8-S-MV
Wiring Diagram 224513
Manufactured July 2004

I see now on a more detailed service manual (Reznor website online) that they recommend a different fan control [kit] depending on if it was made before/after 2004;

I took a look at the wiring diagram and like I said earlier a regular thermostat will not work. This unit has been setup at the factory to be installed with a 3 position selector switch.In the heat mode the fan is energized thru the fan control already installed in unit or can be bypassed and ran continuosly. The temperature is controlled by the Maxitrol Selectatrol, which is a big black knob mounted on the wall. It is a sensor not a tstat that is Dc voltage and controls the signal to the Maxitrol amplifier which then controls the modulating gas valve. I can not tell you how many times I have seen this installation problem. In order to use a regular thermostat the unit needs to be changed control wise internally.

[MUNC]

I took a look at the wiring diagram and like I said earlier a regular thermostat will not work. This unit has been setup at the factory to be installed with a 3 position selector switch.In the heat mode the fan is energized thru the fan control already installed in unit or can be bypassed and ran continuosly. The temperature is controlled by the Maxitrol Selectatrol, which is a big black knob mounted on the wall. It is a sensor not a tstat that is Dc voltage and controls the signal to the Maxitrol amplifier which then controls the modulating gas valve. I can not tell you how many times I have seen this installation problem. In order to use a regular thermostat the unit needs to be changed control wise internally.

well done wiz. i've seen it myself. just like trane units customers want to put stats from home depot on and cant figure why they don't work. reznor make-up air units are just that, make-up air and need to run when building is occuppied

[929rc51]

well done wiz. i've seen it myself. just like trane units customers want to put stats from home depot on and cant figure why they don't work. reznor make-up air units are just that, make-up air and need to run when building is occuppied


I took a look at the wiring diagram and like I said earlier a regular thermostat will not work. This unit has been setup at the factory to be installed with a 3 position selector switch.In the heat mode the fan is energized thru the fan control already installed in unit or can be bypassed and ran continuosly. The temperature is controlled by the Maxitrol Selectatrol, which is a big black knob mounted on the wall. It is a sensor not a tstat that is Dc voltage and controls the signal to the Maxitrol amplifier which then controls the modulating gas valve. I can not tell you how many times I have seen this installation problem. In order to use a regular thermostat the unit needs to be changed control wise internally.


The Reznor unit can not be wired with a typical thermostat, it is designed to have fan run during building occupied hours and heat to cycle with temperature controller. I am very familiar with this unit. Our company does startup and some warranty work for Reznor units. What is the wiring diagram number on the nameplate or the complete model number of the unit.

Great info guys:cheers:

[Anvanho]

Okay, much appreciation for taking to the time to clarify all that.

Thanks!

I should mention that all 4 existing thermostats in this (~6 year-old) commercial office building are all White Rodgers #1F78-151 models .. fairly common unit.

Seems like a pretty standard thermostat.

The other [Reznor] units running here are doing fine [so far] with that thermostat.

(Well, actually one did get updated back a year ago, by the Heating/AC company that assists with HVAC issues here ...)

Will pursue this new information with my tech',

Thanks again ....

pretty helpful bulletin board here.

[acwizard]

Okay, much appreciation for taking to the time to clarify all that.

Thanks!

I should mention that all 4 existing thermostats in this (~6 year-old) commercial office building are all White Rodgers #1F78-151 models .. fairly common unit.

Seems like a pretty standard thermostat.

The other [Reznor] units running here are doing fine [so far] with that thermostat.

(Well, actually one did get updated back a year ago, by the Heating/AC company that assists with HVAC issues here ...)

Will pursue this new information with my tech',

Thanks again ....

pretty helpful bulletin board here.

It is possible that the other units have a different wiring diagram. The unit if somehow someway is running it isn't running properly. More than likely the units are not modulating the heat output and are costing the owner money in operating cost savings.