Pentair Mastertemp immediately flips breaker

Jump to latest Follow Reply
A

ALWPV

In The Industry
Sep 2, 2024
7
New York
Avid reader ( have learned a ton, thank you!); first time poster.

We have a Pentair Mastertemp 400; it is 3-4 years old and we store it inside during the winter. Set up and operating normally this season but at some point it stopped working. When we turn it on, it immediately flips the breaker. (Not sure if relevant, but for some reason, it does not flip the breaker on the electrical panel near the pool, but flips the breaker on the panel in the garage, which the pool panel is connected to.)

There had been a mouse living inside at one point (these things seem to attract them, despite putting mesh around the outside) and some of the wiring had gotten frayed, so I replaced all of the wiring as a first step to fixing the heater since it seemed like the issue was a short caused by an exposed wire.

That did not fix the problem. I have tried a few things to troubleshoot; if I turn it on with the fenwal disconnected (and everything else plugged in) it does not flip the breaker and the heater stays on. If I turn it on with the fenwal connected, but have the fenwal unplugged from the control panel it also stays on. In neither case of course does the heater actually start up.

The funwal does not look damaged in any way, and the fenwal circuit board looks clean. I have ordered a new fenwal but it will take some time to get here.

Is there a way to troubleshoot the funwal and make sure that is the problem and not something further down the circuit? The breaker flips immediately so whatever is causing the problem must be getting energized right away (rather than as it goes through the startup sequence of checking blower, etc). Also I’m not getting any error lights from the control board or the fenwal since the power cuts out immediately. Any other ideas and suggestions welcome!
 
Welcome to TFP.

Show us pictures of both breaker panels and the breakers in the heater circuit.

You sure you have a heater problem and not an electrical wiring problem?

Have you put a clamp on ammeter on the heater power line and seen the amps it draws?
 
Thank you! Not sure if it is electrical or not; without the heater connected, everything runs fine and the heater was working previously. With the general disconnected or connected but not connected to the circuit board, there is power to the heater but it does not start up (as expected). As soon as I make the full connection with the general, the breaker flips immediately.

I don’t have a clip on ammeter but can get one and give it a try.

Attached are pictures of the panel in the garage and then of the pool panel.

Thanks!
 

Attachments

  • IMG_2276.jpeg
    IMG_2276.jpeg
    335.3 KB · Views: 6
  • IMG_2277.jpeg
    IMG_2277.jpeg
    429.2 KB · Views: 6
  • IMG_2278.jpeg
    IMG_2278.jpeg
    287.8 KB · Views: 6
  • IMG_2279.jpeg
    IMG_2279.jpeg
    262.4 KB · Views: 6
Your pool panel does not have any GFCI CBs.

It looks like the breaker in your house panel is a GFCI CB since it looks like the CB has a white TEST button. Please confirm that.

You are probably getting a GFCI trip.

The required GFCI CBs should really be in your pool panel for individual devices and not in the combined feed.

Ground fault losses are additive. The GFCI CB is designed to trip when 4ma is lost. Any one device can lose less then that and it is fine. Turning on your heater may add enough electrical loss to trip the GFCI CB although there are no problems.

I would stop trying to replace parts in your heater. Change your pump, pool cover, and maybe light CBs to GFCI. And change your main panel CB to a non-GFCI CB.
 
Got it - yes the garage panel breakers is gfci and you are right the pool panel ones are not gfci. This is the way the pool installer did it 10 yrs ago but sounds like not the best way.

I will se about putting gfci breakers in the pool panel.

Assuming I do replace all the cbs in the pool panel to be gfci, wouldn’t the fault in the heater still be a problem and cause the breaker to flip? If so, is there a way to isolate where the fault in the heater is coming from? Or maybe I’m not understanding.

Thanks!
 
Open the junction box in the Mastertemp where the power supply connects to the heater wiring.

Shut off all power and disconnect the wiring of the heater to the power supply.

Check each heater power lead to ground for continuity.



1725296520737.png
 
ALWPV said:
Or maybe I’m not understanding.
Click to expand...
It may not be a problem once you get the devices on separate circuits so the ground fault loss is not additive across devices.

ALWPV said:
Assuming I do replace all the cbs in the pool panel to be gfci, wouldn’t the fault in the heater still be a problem and cause the breaker to flip? If so, is there a way to isolate where the fault in the heater is coming from?
Click to expand...

It is very unusual for a heater to have a GFCI trip.

Finding ground faults are not simple and take some detective work and electrical poking around.

Ground faults are caused by water or corrosion being in places it should not be. First thing is to carefully look for water or corrosion around the high voltage electrical areas of the electrical box and the blower motor.
 
I do not like more then one device on a GFCI breaker. It makes it difficult determining which device is causing the GFCI trip.

I would try to move the heater to a dedicated GFCI breaker.

The lower right breaker is not labeled. Is it being used?

The upper right breaker 240V is labeled "Control Voltage". What does that feed? If it only feeds the EasyTouch transformer it can be changed to 120V and a 120V GFCI breaker can be installed for the heater with the heater voltage being changed from 240V to 120V.
 
Ok thanks. You are right those are unused and the control panel has two fuses. Not sure I want to move wires in the fuse box but I understand and appreciate what you are saying.

I did check continuity on the heater leads and I get an OL on the meter (checked on another applicable to make sure it’s working). I did also try to turn the heater on with the cover, lights and outlet fuses off (to make sure they weren’t part of the problem) but it still tripped right away.

When I turn the heater on with the “f1” and “f2” lines disconnected from the fenwal, it does turn the circuit board and screen on, with a service heater light.
 

Enjoying this content?

Support TFP with a donation.

Give Support
ALWPV said:
When I turn the heater on with the “f1” and “f2” lines disconnected from the fenwal, it does turn the circuit board and screen on, with a service heater light.
Click to expand...

That would indicate a problem with the blower motor causing the GFCI trip. F1/F2 powers the blower through a relay in the Fenwal that closes and connects them.

You could have a leaking heat exchanger putting water into the blower motor.

Remove the lower left bolt from the heater manifold and see if any water comes out. If you get any water then your heat exchanger is leaking,
 
Last edited:
I wasn’t sure which was the lower left bolt from the heater manifold so have not checked that yet. If you could point me to a picture of that, I’d appreciate it.

I did test the resistance from the two terminals to ground and those both had resistance, so that’s good - may mean fenwal is ok. The lead that was connected to f1 had resistance, but the f2 lead gave me an OL. When I run the heater with the blower disconnected, it trips (with f1 and f2 connected); it also trips when I just have f1 connected.
 
ALWPV said:
I wasn’t sure which was the lower left bolt from the heater manifold so have not checked that yet. If you could point me to a picture of that, I’d appreciate it.
Click to expand...
1707583879555-png.553549
 
ALWPV said:
The lead that was connected to f1 had resistance, but the f2 lead gave me an OL.
Click to expand...
OL means open line.

All hot wires to ground should read OL.

Any reading for resistance is bad because it means that there is continuity.

Continuity means a path for current to leak.

What was the resistance reading?
 
You must log in or register to reply here.
Thread Status
Hello , This thread has been inactive for over 60 days. New postings here are unlikely to be seen or responded to by other members. For better visibility, consider Starting A New Thread.
Top Bottom
Back
Jump to latest Follow Reply