Max spa temp is only 98 degrees

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khs123
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Joined: Wed 20 May, 2009 14:31
Location: Cincinnati

Max spa temp is only 98 degrees

Postby khs123 » Wed 20 May, 2009 14:46

I have a Pentair "Minimax 400 that is about 10 years old. The heater will only reach a temperature of around 98 degrees then cycles on and off about every thirty seconds. Found the flow control to be broken and have replaced with no change. While I was at it I also replaced the thermistor and it acts the same as it did with the old one. I know the opinion will be to trash it and buy a Jandy but that is not in the budget. I don't know what else it could be except the thermostat board but don't know how to test. Anyone got an idea?

Thanks in advance for the help.
Kirk


Me...
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Max spa temp is only 98 degrees

Postby Me... » Wed 20 May, 2009 15:26

No, trash it and buy a Raypak :lol:

It does sound like low flow through the heater is causing it to cycle on the Hi Limit. I would be looking at it from that angle, not a control but a flow problem. Theoretically the pressure switch should prevent it from even firing in that case but ................................
khs123
Pool Newbie
Pool Newbie
Posts: 2
Joined: Wed 20 May, 2009 14:31
Location: Cincinnati

Max spa temp is only 98 degrees

Postby khs123 » Wed 20 May, 2009 16:58

It runs normally until it hits 98 degrees then it starts to cycle on and off. The service light never comes on. Manual says it will come on if over temp is a problem. Any other thoughts?

kirk
Me...
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Posts: 302
Joined: Thu 26 Feb, 2009 11:11

Max spa temp is only 98 degrees

Postby Me... » Thu 21 May, 2009 09:12

A hi-limit measures water temp as it leaves the exchanger. If it gets over about 140F or so it will shut the heater down until it cools and then automatically reset allowing the heater to fire again. On electric heaters this will be a manual reset.

I am not positive on the MiniMax at the moment but it should have a "Flow Control" which will try to bypass excess water flow to ensure a max velocity through the exchanger. This will prevent erosion of the exchanger. It will simply bypass the excess flow inside the header from the inlet directly to the outlet.

There should be another thermostatic control inside like the hi-limit will that will measure the water temp leaving the exchanger and open or close accordingly to maintain a temperature inside the exchanger at about 120F. This is exactly the same way the thermostat in your car works and in fact will look similar. Cooler and you can get condensation and hotter you will get scaling internally which will plug up the exchanger.

So I would double check which part you replaced. You may not have found the thermostatic control which is what I would still be looking at.

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