Caddy Fan Anomaly?

[NotScot]

Working with a Caddy Advanced, 2 years old and dealing with installation issues related to poor air flow. Long story and the data I am gathering ( including manometer, temperature, and anemometer and thermal data logging ) are addressing the airflow stuff.

There is something else that I personally observed this week and I am seeking any other users who have noted similar issues.

LED Operation Bug?

A few times this year, the owner had me troubleshoot missing LED indications. I eliminated the hardware as a result of a three step (three occurrence) process, and determined that when it appears, cycling the power for 10-15 seconds restores proper operation reliably. This strongly hints at software with the condition cleared on PowerOnReset. ( I am a retired embedded control / test engineer with a few dozen designs under my belt and have seen this sort of thing before. ). Sound familiar to anyone?

Fan Operation Bug?

During debug of the system two days ago, I witnessed the plenum temp go to nearly 300 degrees after restarting the fire. I was measuring static pressures and temperature rise. While waiting for the Caddy fan to restart, the (properly functioning!) LED started fast blink (5 Hz). This indicated that the controller detected AND responded to the overtemp condition. The fan did not run. I reset the power to the unit for about 10 seconds. The LED illuminated properly at first ( advising that heat was available and that the TSTAT was calling for heat). The fan did not run. In a few seconds, fast blink returned, indicating overtemp. It also verified that the controller was functioning and that the plenum temperature sensor was functioning and being properly read.) No fan.

Fortunately, there is another fan upstream of the Caddy and I turned it on manually, and the plenum temp went to 130F quickly. I left it on until the wood was consumed.

Looking at the "schematic" (sic), there are two fuses (serial?) that protect the ECM. I accessed them and checked the fuses. Both were good. I did not remove the fuses and made no configuration changes. Nothing changed except probing two fuses and I intentionally did not disturb any wiring.

At this point, the owner tells me that she has solved this problem before by removing power for 30 minutes? I was very skeptical. However the fuse issue took me about 15-20 minutes to address. When I plugged it back in, the unit operated normally.

As this is a safety critical feature, and since I have suspicions that there is a latent issue elsewhere, I am seeking any observations anyone else has had with this unit. Not trying to pick a fight or start trouble, but this is a "work it until you fix it" issue with me.

 

[3fordasho]

I have the caddy advanced with the 1/2hp ecm motor. I've had similar issues with the blower randomly not kicking on and going into overheat mode (fast flash of the indicator light). I removed the control board and replaced one of the two relays on the board.
Seemed to fix it for a while but the problem came back. Cycling the power worked a few times until it didn't. The intermittent nature of the issue makes it hard to troubleshoot. I even installed a snap switch on top of the plenum that is wired to kick on the propane furnace blower to get some air moving (parallel install) when the caddy blower failed to run. Purchased a spare control board and ECM blower motor but have not installed either since I don't get a complete failure.

This winter it's been working perfectly since I installed an adjustable snap switch on the caddy plenum and use that to independently control the caddy blower - not using the caddy control board to run the fan motor at all. The ECM motor has 110v at all times and runs when the snap switch sends 110v control signal to one of the speed selection wires.

 

[3fordasho]

One more operation bug - When the blower was wired to the control board as intended by SBI, the fan would occasionally stick on and run continuously until power was removed. (power cord unplugged) Normal operation would resume when powered back up.

I did contact SBI service techs several times but they only came back with the most basic troubleshooting info like checking connections to the blower motor, fuses, power and ground connections. To be fair the intermittent nature of the issue does make it difficult. At one point they simply stopped responding to my issue.

One useful piece of info they gave me is the control board only uses one input for fan control, the RTD you mount in the plenum. That checked out perfectly so was able to eliminate that. Other sensors measuring firebox temps are used for primary and secondary inlet control. (technically it also used thermostat input for fan control if there is sufficient heat in the fire box - will run the fan on call for heat from thermostat)

At this point if I had to point to something it would be the control board as the blower motor has been working perfectly since wiring it independently of the control board.

 

[NotScot]

One more operation bug - When the blower was wired to the control board as intended by SBI, the fan would occasionally stick on and run continuously until power was removed. (power cord unplugged) Normal operation would resume when powered back up.

I did contact SBI service techs several times but they only came back with the most basic troubleshooting info like checking connections to the blower motor, fuses, power and ground connections. To be fair the intermittent nature of the issue does make it difficult. At one point they simply stopped responding to my issue.

One useful piece of info they gave me is the control board only uses one input for fan control, the RTD you mount in the plenum. That checked out perfectly so was able to eliminate that. Other sensors measuring firebox temps are used for primary and secondary inlet control. (technically it also used thermostat input for fan control if there is sufficient heat in the fire box - will run the fan on call for heat from thermostat)

At this point if I had to point to something it would be the control board as the blower motor has been working perfectly since wiring it independently of the control board.

I have the caddy advanced with the 1/2hp ecm motor. I've had similar issues with the blower randomly not kicking on and going into overheat mode (fast flash of the indicator light). I removed the control board and replaced one of the two relays on the board.
Seemed to fix it for a while but the problem came back. Cycling the power worked a few times until it didn't. The intermittent nature of the issue makes it hard to troubleshoot. I even installed a snap switch on top of the plenum that is wired to kick on the propane furnace blower to get some air moving (parallel install) when the caddy blower failed to run. Purchased a spare control board and ECM blower motor but have not installed either since I don't get a complete failure.

This winter it's been working perfectly since I installed an adjustable snap switch on the caddy plenum and use that to independently control the caddy blower - not using the caddy control board to run the fan motor at all. The ECM motor has 110v at all times and runs when the snap switch sends 110v control signal to one of the speed selection wires.

hey tim... thanks for that info. dovetails with my observations. which spare control board did you purchase and when? ( the one you are not using? ). i've been looking at this all day today, mostly to get part numbers off components, motors, PCB, etc. step 1 in understanding an embedded controller.... data sheets! i am curious about your spares and when you got them.

i'll share anything I discover, of course. interesting problem and the machine itself is nice.

 

[3fordasho]

Control board is part # PL66213, I purchased in April 2025 and cost was around $200. For what it's worth the caddy advanced and drolet heat commander control boards are the same board and part #.

 

[NotScot]

Great. good to know about the HC. Any interest in selling that board? I am considering building a test fixture to subject the board to repetitive simulated over-temps to precipitate a failure condition to make the problem repeatable and testable. ( Old habits die hard. I did a lot of test engineering back in the day. ) Non-destructive, cheap, fast, and useful. It's the same one that I have based on the missing components, etc. and it might help someone dodge a house fire some day.

 

[NotScot]

Control board is part # PL66213, I purchased in April 2025 and cost was around $200. For what it's worth the caddy advanced and drolet heat commander control boards are the same board and part #.
View attachment 344609

also... if not interested in selling, did you buy it directly from PSI/Caddy?

 

[3fordasho]

I'll hang on to the control board, this furnace is a critical heat source and I like to have spares.

I purchased from : https://www.myfireplaceproducts.com...lectronic-components/electronic-card/pl66213/
(basically the online store for SBI - Stove Builders International is parent company of PSI/Caddy)
Price is the same as what I paid last March.

Sometimes they send out promocodes - they sent me code "GET50" a while back- not sure it's still good but was $50 off your cart at that time.

 

[NotScot]

thanks! that's useful and very much appreciated.

 

[NotScot]

( i initially posted this to the wrong reply. )

Curious as to where you connected your snap switch? I have an external fan that requires a contact closure and plan to use that with the snap switch while I investigate the controller. There are two relays resident on the circuit board and two unpopulated relays. The one that goes to the fan is at the end where the thermocouples connect ( farthest from the input power module ).

The exploded parts diagram in the Caddy manual shows two fan relays that appear to be off-board. The fan clearly runs faster during plenum overheat than it does during normal cycling, leading me to believe that the other relay on the circuit board is a separate speed selection wire going to the ECM fan.

So... not sure I am making this clear, but wondering how you set yours up?

 

[3fordasho]

( i initially posted this to the wrong reply. )

Curious as to where you connected your snap switch? I have an external fan that requires a contact closure and plan to use that with the snap switch while I investigate the controller. There are two relays resident on the circuit board and two unpopulated relays. The one that goes to the fan is at the end where the thermocouples connect ( farthest from the input power module ).

The exploded parts diagram in the Caddy manual shows two fan relays that appear to be off-board. The fan clearly runs faster during plenum overheat than it does during normal cycling, leading me to believe that the other relay on the circuit board is a separate speed selection wire going to the ECM fan.

So... not sure I am making this clear, but wondering how you set yours up?

So I disconnect the s1 - s4 wires at the motor or control board so there is no connection to the control board. I leave the white N and black L wires connected to the control board. Then run an additional wire from Black L connection to one side of the snap switch. From the other side of the snap switch run a wire to one of the speed taps, I think I selected Red S4.

The snap switch I used: https://www.zoro.com/zoro-select-adjustable-fan-switch-90-130-6uee1/i/G3923787/
I mounted the snap switch high on the plenum to the outside sheet metal.

It works pretty well with the adjustable snap switch, but since I have one on hand I will upgrade to this:

McMaster-Carr

McMaster-Carr is the complete source for your plant with over 595,000 products. 98% of products ordered ship from stock and deliver same or next day.

www.mcmaster.com

With this control I can mount a probe inside the plenum, and select the differential I want vs the fixed differential of the snap switch.

 

[NotScot]

Thank you! That's interesting. I have a slightly different strategy in mind that is related to a supplemental gas furnace fan with a FAN ONLY control, low voltage. Have made no mods, yet, but the idea is to make no mods to the Caddy at all. Still working the details. I did get a controller, however, and am inspecting it. Will post results in a few weeks.