Pentair Minimax 100 burner will not light

[swamprat69]

The fact that voltage from TP to the unattached orange wire is 475 mv and the voltage from TP to TH with the orange wire attached to TH is 62 mv is indicative that the gas valve solenoid is stuck closed and the gas valve needs to be replaced .

 

[tjmlack]

Thank you.

 

[swamprat69]

That is assuming that you have adequate gas pressure to the gas valve.

 

[tjmlack]

After looking at the direct replacement from Pentair, is there an alternative gas valve that is available for less that will do the same thing?

 

[swamprat69]

I don't know what price you consider too high but found the replacement listed here for just over $325 Pentair Gas Valve, Mv Mmx 75/100 Nat. Sit (471436) - INYOPools.com

 

[tjmlack]

Thanks. The one I found was $418 on Amazon. Was looking for an alternative equivalent that would work. Is the Pentair gas valve any different then those used for hot water tanks providing the specs are the same?

 

[swamprat69]

I think the original was made by an Italian company. Specs are not too clear but I did notice that it is listed at 4.0" WC rather than the more normal US 3.5" WC. Would considerr it best to use the original or listed replacement.

 

[tjmlack]

Thinking about the operating/safety circuit, if all the components are in good working order, this circuit is just a jumper wire between the TP/TH and TH connection when the demand for heat is there. If I were to disconnect this circuit and put a jumper wire across these connections, TP/TH to TH, would this be a way to test the valve? If the valve opens then I would suspect there is a problem in the operating/safety circuit.

 

[swamprat69]

You are correct, but that would remove all of the safeties and operating controls. As a momentary test it would give you an answer, but it must be only momentarily. Never did ask but is the heater natural gas or LP?

 

[tjmlack]

Finally felt up to crawling under the deck to work on the heater again. This has had me baffled since opening up the pool this Spring also.

Checked the continuity across the operating/safety circuit with connections removed at TH/TP to TH, read 0.00 ohms little bouncing with some low resistance. Thermopile had been replaced. I replaced the pool filter. The heater is natural gas.

Lit pilot flame and watched thermopile mv reading rise up to 426mv. But over time it varied between 411 to 439mv. So mv between TP/TH – TH also varied 319 to 364mv.

Jumpered gas valve from TP/TH to TH and valve opened and burner lit. Removed jumper and burner stayed lit. Would stay lit for about 30 minutes then shut off. Did this several times. Last time I tried to jump start, burner came on but immediately shut off and would not stay lit. Pilot light was still on. Gave up and had a beer.

This is why I’m thinking it may be the valve unless it’s the variation in mv from the thermopile.