MiniMax Plus Heater Won't Fire Up

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MiniMax Plus Heater Won't Fire Up

Postby pzsaul » Sun 14 Jun, 2009 19:19

I have a 7 year old Pacfab (Pentair) MiniMax Plus 150M Natural Gas Heater. It has a Honeywell VS820C1456 gas valve and a honeywell TS8205 electronic control module. The pilot lights and stays lit but the burner will not ignite and fireup when pool is running.
If Idisconnect the TH/PP and TH wire at the electronic module end and jump them together the burner fires up and heater runs but without any thermostatic control. I have swapped out the electronics module and no difference. Could the valve be bad?
Thanks Dion

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MiniMax Plus Heater Won't Fire Up

Postby Gbobbage » Tue 16 Jun, 2009 16:08

If you happen to be in the UK we are about to scrap one of these!

This boiler is quite frankly bloody awful. I guess it may be OK in the hotter parts of the US sited outside in the sunshine but here in the damp, wet, UK it is useless!

I have replaced the amazingly overpriced valve a few years ago, during shutdown the alloy castings corroded up and jammed the valve nicely as I remember. The coils were OK when you measure them with a multimeter. I seem to remember.

I haven't got the boiler next to me so I'm not sure what the TH/PP and TH wire are , but by the sound of it when you do this trick the valve opens so I guess the valve is OK?

From what I remember from one of the times the boiler went wrong is that the control PCB (which was damp!) opens the pilot and fires the sparker when called by the Thermostat IF the flow switch is operating (pump on). Next when the pilot is lit (this is checked by using flame rectification of a current between the sparker and ground, clever!) the main gas valve opens and the burner lights and stays lit providing the flame rectification continues. I think this was how it worked but it is a few years since I looked at this part and yours may be different!

If you're not sure about any of this don't play with it as most of the circuit runs at mains (line in US speak) and the sparker is high voltage.

It may be worth giving the sparker a good clean and the metalwork on the burner around it (you have to take the burner out, a GAS SAFE registered engineer job only here in UK)if the control PCB isn't detecting that flame rectification is working. Does the sparker keep cracking when the pilot is lit?

Binning ours this year after years of trouble and fitting a condensing domestic gas boiler and seperate heat exchanger, possibly some solar too!


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