Clunking noise when heater running

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Ukiwis

Ukiwis

Well-known member
Jul 22, 2018
93
California
I was in the tub this morning and heard this noise. It seems to happen every couple of minutes and is located near the inlet or outlet of the heater. Sound is towards the end of the first video.

Any ideas what this could be and what should be done about it?

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Clunking Noise

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My heater instructions say that you need to increase water flow and adjust the flow sensor to a higher flow rate when you hear that clunking.
 
PoolStored said:
My heater instructions say that you need to increase water flow and adjust the flow sensor to a higher flow rate when you hear that clunking.
Click to expand...
Thanks PoolStored.
The heater is a Mastertemp 250 and I have the manual but don't see those instructions. Can you please direct me to the instructions?

Are these settings appropraite for the Spa?

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Replaced the filter today and no longer have the clunking noise. The heater fires and works correctly and gets to temperature. When temp is reached it shuts off as expected. When the jet pump is turned on the "Service Heater" light comes on and the heater fails to maintain temperature. The AGS LED is lit on the back of the circuit board. If the heater is turned off the light gets reset and the heater will again work, provided the Jet Pump is not running.

I'm going to place a service call with the Home Warranty Co to get it resolved.
 
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Pool tech came and visited and explained it all to me. There are no broken parts. The jet pump is 3HP and is on a dedicted 3" line which is large compared to the filtration circuit...I think he said 2" or 2.5". Anyway, if the heater turns on while the jets are running the heated water cannot escape the heater due to the pressure. The fix was to change the Speed Setting from 2250 to 3250 for the "Spa Heat" setting shown above in VSP Setup.
 

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Does the regular filter water return to the spa through the same returns as the jet pump?

Does the filter pressure go up when the jet pump comes on?

Check the pump RPM, GPM, System Pressure, Filter Pressure and Watts with the Jet pump off and with the jet pump on.

......................................RPM.....GPM.....System Pressure.....Watts.....Filter Pressure
Jet Pump Off.........
Jet Pump On.........


Put the automation into "Service" mode to control the pump from the pump keypad.
 
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Ukiwis said:
Anyway, if the heater turns on while the jets are running the heated water cannot escape the heater due to the pressure.
Click to expand...

Ukiwis said:
The jet pump is 3HP and is on a dedicated 3" line
Click to expand...
If the jet pump is on a separate line, then how does it affect the return flow for the circulation on a separate line?

I suspect that the internal bypass and/or the thermal regulator are probably bad.

Does the heater only have the issue when the jet pump is off?

If the jet pump is off, does the heater work correctly?

Check the stack temperature to see if it is too high.
 
The issue was only present while the JetPump was running. Heater worked fine otherwise. By separate line I meant that the water for the Jetpump comes from the tub and does not go through the filter nor does it go through the heater.

I had the filter speed configured at 2250 rpm for "Spa Heat" so as soon as the heater came on the speed would drop from the 2750 speed setting for Spa to 2250.

The jetpump is a 3HP single speed pump and with the low setting for Spa Heat it was unable to push water through the heater fast enough so the temperature was quickly rising above the setpoint and turning the heater off. With the heater off the filter was flipping back to the Spa speed setting of 2750...this caused the temp to drop below the setpoint and the cycle starting over repeating itself. That's how he described it and it made sense to me.

As soon as the "Spa Heat" Speed was set to the correct setting of 3200 the problem went away.
 
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Where does the water from the filter pump return to the spa?

Does it go through the same jet return fittings as the jet pump?

Can you show a picture of the spa and all of the water inlets and outlets?

Do both pumps pull from the same suction fittings?
 
If both pumps pull from the same main drains, they will be fighting each other for water.

If both pumps are using the same return lines, they will be opposing each other on the pressure side.

Either case is incorrect plumbing.

If they do not use the same suction or the same returns, then the jet pump being on or off should not make any difference.

The heater should work just fine at lower speeds.

So, something is probably wrong with the heater or the plumbing.

Can you check the information that I referred to?
 
@JamesW
Both pumps do pull from the same Drains.
Both pumps do return to the same jets in the tub.

Arrows show flow to/from jet pump.

1634653496262.png

Given that everything feeds the same jets I guess they connect somewhere underground.

The filter shows 20 PSI when the Spa is on.
The filter shows 30 PSI when the Spa is on and the jet pump is on.
 
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Ukiwis said:
Both pumps do pull from the same Drains.
Both pumps do return to the same jets in the tub.
Click to expand...
That was a huge mistake.

That's just bad design.

If you have a separate jet pump, it needs to have it's own suction and returns.

I would get rid of the extra pump and just use the filter pump.

You can put a spring bypass on the heater to automatically bypass excess flow around the heater.
 
You can put a 3 lb check valve bypass to bypass excess water around the heater.

A 2 lb check valve would probably work, but it's close, so a 3 lb. check valve would be better for margin.

A check valve bypass stays closed until the pressure hits the rated pressure and then the valve begins to open.

All of the water will flow through the heater until the flow gets to about 40 gpm and then the pressure will be enough to begin opening the spring check valve, which will begin bypassing excess water around the heater instead of forcing it through the heater.
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@JamesW thanks for the detailed reply. I've had no issues for 3 years so I shouldn't need to add any valve, should I? I did change the VSP speed settings some time ago to try and save some energy. I thought yesterday when all this was explained to me that the problem has probably existed for 6 months or so but I've only noticed it now.

I thought this was all resolved yesterday with the speed change but on using the tub this morning, I'm now getting the Service Heater light coming on when the heater is running at the same time as the Jet Pump. I called the tech that visited yesterday thinking he'd come back and handle the AGS light and perhaps replace the sensor, but he said there is nothing wrong with the heater. It heats and turns off when it gets to temp and cycles on/off as it's supposed to do . The service heater light coming on is due to the fact that I'm turning on the Jet Pump and by doing so I'm "introducing" the problem.

He contacted Old Republic and they are sending a second Co for a 2nd Opinion.

#FUNTIMES

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The system was not designed or installed correctly from the beginning.

You can’t have the jet pump on the same suction and returns as the filter pump.

That will not work.

I would get rid of the jet pump and just use the filter pump.

Connect the suction to the filter pump suction and connect the returns to the filter returns.

I would put a 3 lb. (3 psi) spring check valve bypass on the heater.
 

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