Raypak Heater temperature incorrect

[Malcolm3]

I have a Raypack P-R266A-EN-C heater that I am having difficulty trouble shooting. The heater turns off prematurely as it reads the temperature higher than the actual pool water. After doing some reading I thought maybe this was a faulty temperature probe which I could replace. However when the heater is not on it reads the pool water temp correctly. Then after about 30 minutes of being on (heater temp set to 85), it says the pool water is 85 and turns off, when in fact the water has only gone up about 1 deg, to 77.7F. Since it is reading the initial water temp correctly I'm not sure if it could be the temp probe causing this issue. Any other things that I should be checking?

 

[mas985]

Some background information would be useful.

When did this particular issue start?

Has it ever worked properly?

How old is the heater?

What is the filter pressure when the heater is running?

Are your running the pump at lower than full speed?

What is the make/model of pump?

If running at lower speeds, try running at a higher RPM and see if the problem goes away.

 

[Malcolm3]

Some background information would be useful.

When did this particular issue start?

Has it ever worked properly?

How old is the heater?

What is the filter pressure when the heater is running?

Are your running the pump at lower than full speed?

What is the make/model of pump?

If running at lower speeds, try running at a higher RPM and see if the problem goes away.

The heater is 10 years old. It worked properly last season. This is a new problem when I opened the pool this spring. My filter pressure runs between 15-25 psi then I backwash (25in sand filter). I have a single speed Hayward 1HP pump. I calculated my total dynamic head with the heater in the circuit so I know my pump is moving about 51GPM which is appropriate per the heater manual.

 

[mas985]

The heater is 10 years old. It worked properly last season. This is a new problem when I opened the pool this spring. My filter pressure runs between 15-25 psi then I backwash (25in sand filter). I have a single speed Hayward 1HP pump. I calculated my total dynamic head with the heater in the circuit so I know my pump is moving about 51GPM which is appropriate per the heater manual.

How did you determine head loss?

Is the pump a Hayward 1 HP SuperPump?

What is the current filter pressure?

 

[Malcolm3]

How did you determine head loss?

Is the pump a Hayward 1 HP SuperPump?

What is the current filter pressure?

I used TDH = vacuum x1.13 + pressurex2.31.
I took a vacuum reading before the pump and pressure reading after the pump.

Hayward MaxFlow 1HP.

Current filter pressure is 15psi

 

[mas985]

When you replaced the temperature sensor, did you also remove the bypass valve for inspection and/or remove the manifold for inspection.

Assuming the temperature sensor is working correctly and given the age of the heater, there could be an issue internally with the heater where hot water is getting recirculated back into the inlet somehow.

Can you also post a picture of your pad equipment?

 

[Malcolm3]

When you replaced the temperature sensor, did you also remove the bypass valve for inspection and/or remove the manifold for inspection.

Assuming the temperature sensor is working correctly and given the age of the heater, there could be an issue internally with the heater where hot water is getting recirculated back into the inlet somehow.

Can you also post a picture of your pad equipment?

I haven’t replaced the temp sensor yet. Should that be my first step? It does read the initial water temp correctly. I was planning to replace the temperature sensor since that seems easy enough; just wasn’t sure if there was something else obvious before I started ordering parts.

I suppose if a new temperature sensor does not fix the problem- As you say, I should inspect the bypass and manifold. Perhaps the bypass is broken or the manifold outflow is clogged with scale.

I’ll post a picture tonight.

 

[mas985]

I agree that if the temperature sensor reads the correct temperature when the heater is off, it is probably operating correctly.

It is likely a thermal issue getting translated back into the area of the temperature sensor.

The other possibility is the thermal regulator. Basically, anything in the manifold could be causing the issue.

Does the heater have an external bypass?

 

[1poolman1]

I haven’t replaced the temp sensor yet. Should that be my first step? It does read the initial water temp correctly. I was planning to replace the temperature sensor since that seems easy enough; just wasn’t sure if there was something else obvious before I started ordering parts.

I suppose if a new temperature sensor does not fix the problem- As you say, I should inspect the bypass and manifold. Perhaps the bypass is broken or the manifold outflow is clogged with scale.

I’ll post a picture tonight.

Least expensive thing to try is the temp sensor. Not unusual to read correctly until the water gets warmer. At 10 years old it likely has a crack that opens when the probe get hotter and allow water into the sensor. Also, that is a dual sensor (that's why three wires) so one side can be bad.

 

[Malcolm3]

When you replaced the temperature sensor, did you also remove the bypass valve for inspection and/or remove the manifold for inspection.

Assuming the temperature sensor is working correctly and given the age of the heater, there could be an issue internally with the heater where hot water is getting recirculated back into the inlet somehow.

Can you also post a picture of your pad equipment?

I haven’t replaced the temp sensor yet. Should that be my first step? It does read the initial water temp correctly. I was planning to replace the temperature sensor since that seems easy enough; just wasn’t sure if there was something else obvious before I started ordering parts.

I suppose if a new temperature sensor does not fix the problem- As you say, I should inspect the bypass and manifold. Perhaps the bypass is broken or the manifold outflow is clogged with scale.

I’ll post a picture tonight.

 

[mas985]

Least expensive thing to try is the temp sensor. Not unusual to read correctly until the water gets warmer. At 10 years old it likely has a crack that opens when the probe get hotter and allow water into the sensor. Also, that is a dual sensor (that's why three wires) so one side can be bad.

The sensor is on the inlet side of the heater so it should not change temperature until the incoming water from the pool changes temperature which takes far longer than the time it takes for the heater to shut down.

I think the fundamental issue is that hot water is somehow getting back into the inlet side of the heater which is should not do.

It looks like from picture the blue handled valve of the bypass is open. Have you tried closing that valve?

If left fully open, too little water may be flowing through the heater and it just heats up exchanger which in turn will heat up the surrounding components including the temperature sensor.

 

[Malcolm3]

The sensor is on the inlet side of the heater so it should not change temperature until the incoming water from the pool changes temperature which takes far longer than the time it takes for the heater to shut down.

I think the fundamental issue is that hot water is somehow getting back into the inlet side of the heater which is should not do.

It looks like from picture the blue handled valve of the bypass is open. Have you tried closing that valve?

If left fully open, too little water may be flowing through the heater and it just heats up exchanger which in turn will heat up the surrounding components including the temperature sensor.

Yes when I turn the heater on I close the bypass.

I think I will take apart the manifold and see if water is getting across somehow.

 

[mas985]

Check both the internal bypass and the thermal regulator valves. Either one or both could have an effect on the temperature at the sensor location.