Pentair Mastertemp 400 Question - lower enclosure insulation

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kcheves

Member
Feb 8, 2022
6
San Diego CA
Greetings!

Like many, I had a rat infestation in my Pentair Mastertemp 400 heater. Turns out that the damage was minimal, some gnawed wires on the igniter and flue temp sensor, and they chewed through the blower orifice grate. I was able to get all those things fixed, and the heater now works. Because they ate through the orifice grate I was concerned they had nested in the combustion chamber, so I I opened it up it and (thankfully) found no evidence that the rats had been there.

When I cleaned out the heater and removed the combustion chamber, I found remnants of the insulation pad that goes between the combustion chamber and the bottom tray of the heater. This is Pentair P/N 42001-0074S, Lower Enclosure Insulation.


It’s a circular-ish piece of foil-backed insulation, and rather than buying the OEM part I intend to fabricate a replacement for this when I put the heater back together.

My question for the TFP mind trust is simple; do I install this part with the foil surface facing up or down? I would assume down to keep surface moisture from soaking the insulation, but I could make an argument for up, as well.

Thanks in advance for your help. The Mastertemp troubleshooting articles here made the job pretty simple. While I was in there, I installed the MK rat-proofing kit and put some mothballs inside to prevent future intrusions.

Kit
San Diego, Ca
 
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I’m getting ready to reseal the combustion chamber of my Mastertemp 400 heater following some repairs. The existing red O-ring is in good shape, and I’d like to reuse it if I can.

The kit that Pentair sells is P/N 77707-0120, and includes the O-ring and a tube of Loctite gasket forming RTV. Do I need to use RTV if I’m re-using my O-ring, and if so, would I just apply it to the exposed surface of the gasket, which is currently in the groove on the combustion chamber tub?

Or is this a bad idea, and I should just spring for the gasket kit?

I have the older style combustion chamber (2009-2011) that uses a clamp to compress the combustion chamber lid to the tub, if that makes a difference.

Thanks in advance!
 
kcheves said:
I’m getting ready to reseal the combustion chamber of my Mastertemp 400 heater following some repairs. The existing red O-ring is in good shape, and I’d like to reuse it if I can.

The kit that Pentair sells is P/N 77707-0120, and includes the O-ring and a tube of Loctite gasket forming RTV. Do I need to use RTV if I’m re-using my O-ring, and if so, would I just apply it to the exposed surface of the gasket, which is currently in the groove on the combustion chamber tub?

Or is this a bad idea, and I should just spring for the gasket kit?

I have the older style combustion chamber (2009-2011) that uses a clamp to compress the combustion chamber lid to the tub, if that makes a difference.

Thanks in advance!
Click to expand...
New silicone won't stick to old. All of the old has to be removed. It has to flow as the cover is installed in order to seal properly, so new red RTV is absolutely needed to be safe.
You're dealing with an item that can have a temperature of 2000 degrees (yes, two thousand) in the combustion chamber. The combustion chamber is under pressure when it is lit. You don't want that heat to escape anywhere into that heater.
 
Let's see if @1poolman1 @swamprat69 has dug that deep into a MasterTemp and remembers.

Look at the way this picture shows the insulation...

LOWER ENCLOSURE INSULATION KIT (42001-0074S) - INYOPools.com

LOWER ENCLOSURE INSULATION KIT (42001-0074S) - Pool & Spa Parts
www.inyopools.com www.inyopools.com

6290-540-02.jpg
 
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Thanks for the comments. I think the above comment is correct and the insulation is installed foil side up. We were able to see this in some of the videos in replacing the heat exchanger. That’s the way I did it when I put the heater back together.
 
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