Pentair 250M Minimax Heater

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danpik said:
That is a pretty low reading. Make sure the thermopile is in the pilot flame real good and you have a strong flame. Also make sure there is no corrosion on the leads which would give a low reading as well. If all that is good then I would suspect the powerpile to be weak. I have pulled them out before and tested them in the burner on my gas stove to be sure. Idealy you should see 750 Mv if it is good. They will range a bit above or below that number... 600-800 out of the box.
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I installed a new thermopile, lit the pilot, turned the heater switch to on, and the heater fired right up. My new thermopile is only getting about 520 mV, but it's working fine for me.
 
danpik said:
In your last picture there is a wire (two conductors, red/white) hooked to the gas valve coming in from the right side. The white is hooked to the TH/PP terminal and the red is connected to the PP terminal. That is your powerpile wire. To test it, hook the leads of your meter to each of those. It can be done with them connected but it is better unconnected. Looking at the pictures again you may want to clean up all of the connections as any slight corrosion will cause resistance in the circuit and the voltage is very low on this type of system. If you find that the Milivolts is good then another test to try is to bypass the control circuit by hooking a jumper between the TH/PP terminal and the TH terminal. If you have a good powerpile and gas valve the burners should fire right up. If this happens then you have a bad sensor somewhere in the wire going out from the TH/PP terminal and back to the TH terminal.
In the image I posted the "D" terminal is the same as your TH/PP terminal, "E" is your PP term, and "F" is your TH term. Part 5a and 5c is your powerpile.
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My heater stopped working again last week. The thermopile was only putting out about 450mV, so I took it out and tried turning it so the pilot would hit the other side of the thermopile and I got up to about 500mV and the heater kicked on again.

However, today the heater wouldn't turn on again. I was still getting about 500mV. So I tried jumping the controls like mentioned and it fired right up.

So, if I understand correctly, either the controls or the pressure switch are not working. When I turn the temperature control up and down, I can hear a click when it goes past the temperature of the water. So I'm thinking this means the problem must be the pressure switch? Is there any way to confirm this before buying a new switch?

Thanks,
Cody
 
If you think it's the pressure switch you can disconnect it and using a jumper wire connect the two ends from the switch together. Also make sure you have a clean filter and good water flow in the pool.

At some point it becomes futile to keep something of this age going and tinkering with it every time you want to use it. That's just my opinion.
 
armstrr said:
If one were to decide to quit tinkering with this vintage of equipment, what would you suggest as a replacement?

Lochnivar energy rite?

Raypak/rheem digital?

Sent from my Nexus 5 using Tapatalk
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I use nothing but Raypak/Rheem. By far a better quality unit on the market these days.

Not many residential folks use the Lochinvar plus they aren't cheap.
 
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