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Pentair MiniMax NT-400 not lighting off

Posted by contraption (My Page) on
Fri, Sep 23, 11 at 2:55

I've got a Pentair Mini-Max NT 400kbtu heater from around 2002 (I know, I know, but really, it's been good) that won't light off. It gets pretty heavy (nightly) use year round since new.

Tonight, no go. The red Service light is on. I immediatelly guessed it was a bad igniter, so I removed the igniter and ohmed it out - 141 ohms. This is right within the specs I've seen online (50-300 ohms).

I put it back together, and turned it on again. The system comes on, blower runs, igniter glows, valve clicks, (smell the usual small amount of gas), but then the valve clicks OFF 2-3 seconds after opening, without it firing up. It will cycle a few more times but it doesn't light.

I am able to spark it up with a BBQ igniter while the gas is flowing, and it seems to run fine after that (but won't re-ignite on its own).

I did notice, however, that when it is firing, the "central burner pipe" (the one just under the igniter position) is NOT aflame. All the tubes on either side (maybe 4 per side?) are firing and look good.

Once firing, I AM able to light the jet firing into the open tube (just off the horizontal gas manifold). The flame burns in the "air gap" (open area just after the jet), but the main burner tube associated with that middle jet does NOT ignite.

I haven't ripped into the burner system as yet. Anyone seen this before? Am I headed for a burner assembly replacement, or something else? Is this condition repairable (i.e. cleanable), or is it a rip-n-rebuild project?


Follow-Up Postings:

RE: Pentair MiniMax NT-400 not lighting off

Sounds like spider webs or corrosion in the orifices. Open it it up and see.


RE: Pentair MiniMax NT-400 not lighting off

Have you checked the codes off of the controller?

RE: Pentair MiniMax NT-400 not lighting off

My MiniMax is so old it doesn't have a controller with any type of display - so, unfortunately no codes to work from.

However, poolguiynj - you nailed it. I pulled out the middle jet and tube...and as soon as I turned over the jet a very chunky spider ran out. He left behind a pretty tough web in the orifice - I guess it was enough to restrict the flow so that that the burner under the igniter wasn't getting enough gas.

I took the opportunity to blow some soot and dust out of the burner array while I was at it.

I'm expecting it to work tonight!

Thanks for the help!

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