Help Needed: Fan Motor Delay Relay broken on Thermo Sphere Electric Heater Model EH-4610

[RobinHood]

I‘ve had my electric shop heater since the fall of 2021. Yesterday I noticed that the fan was running continuously - even when the heating elements were off.

Heater Details:

Thermo Sphere Heavy Electric Utility Heater
Model: EH-4610

Here is the data plate:


It was bought at PA and has been working well. Investigation showed that the Motor Delay Relay (MDR) has its contacts closed continuously because the capillary tube has a pin hole in it and all the liquid escaped.



The relay is basically a temperature sensing device between the fins. When the thermostat calls for heat, the heater coil relay closes and the resistive elements start heating up. When a certain temperature is reached, the fan motor is turned on by the MDR. When the thermostat pre-set temperature is reached, the heater coil relay cuts out the resistive heating elements, but the fins are still hot. The fan motor keeps running until they are cooled below a certain temp, again sensed by the MDR which then opens its contacts and shuts the fan off.

The capillary tube of the MDR is installed as such (fins pried open for removal and visibility)



The tube was bent incorrectly at installation in the factory and rubbed on the rear of one of the fins. Since I “opened” the fins in the front, there is clearance - as shown in the picture. There was not when the fins were bent shut to capture the capillary.



The MDR


And an image of the pin hole


Here is the data on the MDR


Here is the website of the manufacturer and specifications of the MDR

AuOne Electrical Co., Ltd

www.auone.com

I contacted the Service email and Tech Support in Boucherville, QC, they have no parts and can’t get any either.


I am asking for help finding either a direct replacement or something equivalent.

Or can the capillary tube be repaired (I think I can solder the pin hole shut) and liquid (I think there is alcohol in those tubes) put back in? Has anyone successfully repaired something like this?

For now I have wired the fan motor to an auxiliary contact on the heater coil contactor. Fan runs when resistive heaters are on (as controlled by the thermostat). My worry is that the elements will burn out prematurely as they are not fan cooled upon shutdown - this is what the MDR is for.

Thanks in advance for your time.

 

[YotaBota]

You could retro fit a "Delay Off" timer and just have the fan start with the element. The local electrical or heating guys may have something or Amazon has a bunch of different voltage/amp modules.

 

[Tecnico]

For parts, do you have an HVAC part supplier in your locale? Wolsey? Master? They might be able to fix you up with an equivalent.

If they're used in baseboard heaters chances are ther'll be stock. Might need to Google a bit for an equivalent part. On that, if you search capillary thermostat there are a bunch of options that might be adaptable, you may have to tweak the settings to get it to turn on/off at the right temp. Maybe something like this:

Capillary Thermostat

I think you said the heater is from PA, will they take it back or exchange it for another model? They're pretty good with returns.

Hope that's useful......

D

 

[RobinHood]

Thanks @Tecnico , I will look into that.

@Dabbler and I had a good conversation regarding my problem. The advantage of staying with an OE capillary thermostat relay is that if it fails, it fails safe into the “ON” position - like mine did. Yes, the fan runs continuously, but at least the elements don’t overheat and possibly burn out.

A time delay relay may not offer that protection. It would function well enough for this application once the times are set. Thanks for suggesting that @YotaBota . It might be the easiest way to go as they are plentiful. Probably would change the circuit to prevent the elements from energizing in case of a time delay relay failure…

 

[ShawnR]

Sounds like a job for @Brent H 's boy, Greg. Perhaps he can advise on parts.....hopefully he chimes in.

 

[TorontoBuilder]

I‘ve had my electric shop heater since the fall of 2021. Yesterday I noticed that the fan was running continuously - even when the heating elements were off.

Heater Details:

Thermo Sphere Heavy Electric Utility Heater
Model: EH-4610

Here is the data plate:
View attachment 31889

It was bought at PA and has been working well. Investigation showed that the Motor Delay Relay (MDR) has its contacts closed continuously because the capillary tube has a pin hole in it and all the liquid escaped.

View attachment 31899

The relay is basically a temperature sensing device between the fins. When the thermostat calls for heat, the heater coil relay closes and the resistive elements start heating up. When a certain temperature is reached, the fan motor is turned on by the MDR. When the thermostat pre-set temperature is reached, the heater coil relay cuts out the resistive heating elements, but the fins are still hot. The fan motor keeps running until they are cooled below a certain temp, again sensed by the MDR which then opens its contacts and shuts the fan off.

The capillary tube of the MDR is installed as such (fins pried open for removal and visibility)

View attachment 31898

The tube was bent incorrectly at installation in the factory and rubbed on the rear of one of the fins. Since I “opened” the fins in the front, there is clearance - as shown in the picture. There was not when the fins were bent shut to capture the capillary.

View attachment 31895

The MDR
View attachment 31892

And an image of the pin hole
View attachment 31893

Here is the data on the MDR
View attachment 31897

Here is the website of the manufacturer and specifications of the MDR

AuOne Electrical Co., Ltd

www.auone.com

View attachment 31900

I contacted the Service email and Tech Support in Boucherville, QC, they have no parts and can’t get any either.
View attachment 31894

I am asking for help finding either a direct replacement or something equivalent.

Or can the capillary tube be repaired (I think I can solder the pin hole shut) and liquid (I think there is alcohol in those tubes) put back in? Has anyone successfully repaired something like this?

For now I have wired the fan motor to an auxiliary contact on the heater coil contactor. Fan runs when resistive heaters are on (as controlled by the thermostat). My worry is that the elements will burn out prematurely as they are not fan cooled upon shutdown - this is what the MDR is for.

Thanks in advance for your time.

You cannot repair them one the liquid inside has escaped.

 

[Garyt]

This may or may not be a solution but interesting

1933 Plymouth Temperature Gauge Repair

A site devoted to the restoration, repair and driving of 1930's Plymouth automobiles.

www.ply33.com

Gary

 

[RobinHood]

Thanks @Garyt . That is an interesting repair.

My issues, if I attempted that, would be calibration. The OE specs do not give the cut-in and cut-out temps; I’d be guessing. All we know is the max temp is 150*C.

 

[Brent H]

@RobinHood - I sent an image of the unit to my son, we may have something in the basement or he can recommend a replacement

 

[RobinHood]

Thanks @Brent H .

 

[Brent H]

@RobinHood : Greg will check his stuff and I will let you know. He is out framing a house right now

 

[Garyt]

Thanks @Garyt . That is an interesting repair.

My issues, if I attempted that, would be calibration. The OE specs do not give the cut-in and cut-out temps; I’d be guessing. All we know is the max temp is 150*C.

Of course calibration woud be a issue but a couple of trials might get you into a workable zone

 

[Tecnico]

This may or may not be a solution but interesting

1933 Plymouth Temperature Gauge Repair

A site devoted to the restoration, repair and driving of 1930's Plymouth automobiles.

www.ply33.com

Gary

Very interesting, I've wondered how they build up those assemblies.

D

 

[RobinHood]

UPDATE:

Thanks to a member for reminding me that I left this thread “hanging” with me temporarily wiring the fan to the aux lugs of the power contactor.

You could retro fit a "Delay Off" timer and just have the fan start with the element.

I did in fact follow @YotaBota ’s suggestion about 5 months ago, and bought a “time off“ (multifunction) relay. I now use the N/O AUX lugs on the main power relay to trigger the new relay.

The fan starts with the heater element ON command and when the thermostat calls for “heat -off” and the AUX contacts open, it triggers the input signal on time delay relay and starts a counter. I have this “off-time delay” set for four minutes. Gives the elements plenty of time to cool off before the fan stops.

I’ve been running the heater in the new configuration since the fall - works great, no issues whatsoever (probably just jinxed myself…).

Aside from the relay, I bought some DIN rail to mount the relay and used on-hand wires and ferrules to make up the new circuits.

Here is the relay I bought off Amazon.


Thanks again for everybody’s help. Much appreciate it.