Mastertemp 400 Gone!

[JoyfulNoise]

Also note that with a flow switch addition you can leave the pressure switch in place and then just wire them in series. That way the pressure and flow switch have to both be satisfied to let the heater fire up. You can consider it a redundant safety switch. Your choice if you want to do that or not.

 

[wgipe]

Also note that with a flow switch addition you can leave the pressure switch in place and then just wire them in series. That way the pressure and flow switch have to both be satisfied to let the heater fire up. You can consider it a redundant safety switch. Your choice if you want to do that or not.

This is exactly what I did. A dealer came out to do some warranty work last fall and really liked the setup - I was a little concerned he would give me a hard time.

Also - in a testament to what I've learned here, he assumed that because of the issues we've had that it hadn't been used based on the condition. When I told him it runs every day, he almost didn't believe me - said it looked better than some of the new ones he pulls from a box. No sign of corrosion whatsoever - even in saltwater. I think it blew his mind.

 

[JamesW]

This is exactly what I did.

Your design is good because it prevents firing without flow.

Because you have a bypass, you can easily get a situation where there is pressure but no flow and it only takes a single mistake to destroy a heater.

In my opinion, it is idiotic for manufacturers to use a pressure switch and not a flow switch.

 

[wireform]

Just to update:
In the linked post (I'm on the sidelines due the pb still in charge for warranty purposes)
Mastertemp 400 Gone!
the heater was giving problems and removing the bottom left screw on the manifold proved a boat load of water exiting. The pb under pentair warranty changed out the heater on Friday and below are the pictures. Pb claims he pressure tested the heater core prior to it removal and it failed miserably.


Now onto the heater I was dealing with on another pool, I did a chlorine test on the drip coming out of the manifold hole which tested about the same FC as the pool water which means the heater core is compromised. From what I could see in the pictures above, both the plumber and the pb are in agreement that condensation from running in the winter ate through the coils. At this point I'm looking at another one of Pentair's pool heaters which is a
condensing heater which will eliminate this problem supposedly.

 

[JoyfulNoise]

….At this point I'm looking at another one of Pentair's pool heaters which is a
condensing heater which will eliminate this problem supposedly.

That heater is going to condense flue gas. It has a double heat exchanger design where the combustion exhaust preheats the water before it going into the main heat exchanger. The preheater will cool the exhaust gas a lot and cause rapid condensation. This is how a lot of efficient gas driven tankless water heaters operate. The condensate will need a special drain line and you’ll need to likely install some kind of neutralizing (alkaline) filter on it or else the nitric and sulfuric acid present on the condensation will destroy everything … even plastic.

It’s a much more complicated heater to service when there are faults so you’d better be comfortable with working on it and Pentair better be able to help you out. They are not at all simple systems to debug.