Pentair MasterTemp 400- recycling and no error code

[Aztully]

Our Penair 400 MasterTemp gas heater turns on but shortly after starting begins to recycle (it makes a lot of banging noises in the process) The temperature reading on the unit will also go rapidly up/down when the unit is cycling. It will then fire up again only to cycle off with the same noisy/banging noise. I have a manual Jandy valve on the inlet side that is partially turned preventing full water flow into the unit. I’m not sure why this valve is necessary or why my pool servicing co has it set where it is currently set.

I’m not sure if I have an equipment problem or a water flow issue. What’s the proper water flow into the unit and how do I properly set if the problem is incoming water flow?

I appreciate, in advance, any help!

 

[ps0303]

Yes check the water flow. Open the valve all the way and see how the unit reacts. Have you cleaned your filter lately? A dirty filter can reduce water flow to the unit. If all of that check out OK and you still have issues then it sounds like a broken bypass. A broken bypass is not allowing enough water to flow into the heater and thus the water that does flow into it boils and thus the knocking and banging. The Jandy valve you have is to allow water to bypass the unit. Sometimes the water flow is too great thus bypass some of it.

 

[jojoman]

I don't have the banging noises but mine is doing the same thing. First it's miss reading the temperature. The read out will say the water is 102F but a thermometer in the spa reads 87F. Then when it gets near the set temperature it starts to go rapidly up/down on the display and switching on/off. Is there something that a user can do to check these kind of problems?

 

[ps0303]

I don't have the banging noises but mine is doing the same thing. First it's miss reading the temperature. The read out will say the water is 102F but a thermometer in the spa reads 87F. Then when it gets near the set temperature it starts to go rapidly up/down on the display and switching on/off. Is there something that a user can do to check these kind of problems?

Yours could be a bad thermistor since the temp reading is off. I would also check the thermal regulator as well. On/off? The unit actually power cycles?

 

[jojoman]

Yes, it comes on and starts heating the water until it gets near the preset temperature then the display starts jumping up and down within a 5 degree range of what it thinks the water temperature is(it's wrong on that account also) and starts clicking turning on and off. I was thinking it is some kind of sensor problem or the like. Would you know if these kind items can be found on the internet and can an owner change the parts out themselves? Thanks!

 

[ps0303]

Yes, it comes on and starts heating the water until it gets near the preset temperature then the display starts jumping up and down within a 5 degree range of what it thinks the water temperature is(it's wrong on that account also) and starts clicking turning on and off. I was thinking it is some kind of sensor problem or the like. Would you know if these kind items can be found on the internet and can an owner change the parts out themselves? Thanks!

First thing is check all the wiring inside and make sure you didn't have a mouse inside chewing on things. Then look at the control board and see if there is corrosion on it. The issue you are having might be a real hunt to find out the cause.

 

[jojoman]

Thanks! Funny you said mouse. One of my neighbors who has a MasterTemp 250 back on New Years said he had a mouse/rat family living in his. Should have been a cue for me to check mine also.