Pentair Minimax 250 - Transformer Burned (literally)

tb40

Active member
Nov 9, 2017
27
Yorba Linda
Minimax 250 spa heater (older model) was working fine for some time, then sporadically for a day or two, then quit completely.

Upon inspections, there were no lights on the control panel, and it didn't take too much detective work to figure out what happened (see photo below).

Questions:
  • Can anyone confirm that "Pentair 471360 Dual Voltage Transformer" is the correct replacement part?
  • Do I just cut power to the unit, then wire in the new transformer?
  • What are the chances that the main control board or other components were damaged as the result of this event?
  • Any other considerations?
Thank you in advance for any assistance you might be able to offer!


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Pool Clown

In The Industry
Sep 5, 2008
2,127
Silicon Valley, CA
Start with replacing the transformer. Disconnect primary side and confirm the AC voltage. four wires come off the primary side. If just the black and the red are connected to the line, that would suggest 220V otherwise it would be 110V. New transformer should come with a wiring diagram to hook up.
 

tb40

Active member
Nov 9, 2017
27
Yorba Linda
Start with replacing the transformer. Disconnect primary side and confirm the AC voltage. four wires come off the primary side. If just the black and the red are connected to the line, that would suggest 220V otherwise it would be 110V. New transformer should come with a wiring diagram to hook up.
Awesome, thanks for the info - I will let you know how it goes!
 

tb40

Active member
Nov 9, 2017
27
Yorba Linda
So I'm assuming I just follow the existing wiring pattern red & black to the two incoming red wires, then cross wire the other two white/red and white/black wires to each other with a wire nut?
IMG_0915.jpg

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Pool Clown

In The Industry
Sep 5, 2008
2,127
Silicon Valley, CA
Yes, rewire one wire at a time. That way, its easy to keep the wiring straight. And before you put power to it, make sure all the rest of the wiring throughout the heater is intact. Nothing disconnected, or burnt, melted, chewed, etc.
 

tb40

Active member
Nov 9, 2017
27
Yorba Linda
Thanks for the reply Pool Clown.

I did some additional research and talked with my brother who has some electrical expertise, and got a little further, see updated info below.

Per you instructions Pool Clown, I put a meter on the wires coming into the heater housing, and confirmed its 220v:
IMG_0920.jpg
The info on the new transformer indicates that for wiring for 220v, I should connect the white/red and the white/black to the incoming power leads. The other wires would remain unused:
IMG_0921.jpg

My plan now is to wire according to the specs on the transformer, turn power on to the unit, then put my meter on the blue output DC spades (not connected downline to the unit yet.) and ensure its kicking out 24V DC.

Good plan, or am I missing something?
 
Last edited:

Pool Clown

In The Industry
Sep 5, 2008
2,127
Silicon Valley, CA
NO NO! White with red stripe connects to the white with black stripe for 220V
Just like yours is now.

Supply voltage is commonly called Line. Third line of text says "line is black and red" WITH (following line) wht with red and white with black connected together.
I know, its a bit vague.
 

tb40

Active member
Nov 9, 2017
27
Yorba Linda
NO NO! White with red stripe connects to the white with black stripe for 220V
Just like yours is now.
Thanks for the reply.

ok, so connect the two stripped wires to each other, then connect the solid wires on the transformer to the wires coming into the housing. Right?

Also, with AC there is no way to wire it “backwards” right?

really appreciate your help!
 

tb40

Active member
Nov 9, 2017
27
Yorba Linda
Right, and right.
Thank you so much for your help! I wired the new transformer according to your instructions, and the unit fired right up! That’s the fantastic news!

Now a new issue has come up, I’m assuming that the wire that was damaged/ burned as the result of the transformer catching fire was the “remote” control wire.

So now the unit ignores the compool control automation panel in our house, and must be turned off manually at the control panel on the actual heater.

I downloaded the instruction manual for the heater, and oddly I couldn’t find any section that discussed the remote wire or wires. Can someone explain how this works? Do I just simply replace the section of damaged wire? Is it just a single wire that sends or doesn’t send a signal. Thanks!
 

Pool Clown

In The Industry
Sep 5, 2008
2,127
Silicon Valley, CA
Right. The wire connects or closes the safety circuit and allows the heater to continue with its call for heat routine. If you can identify the burnt wires, just hook them back up. Should be two, and are not polarity sensitive.
 

tb40

Active member
Nov 9, 2017
27
Yorba Linda
Right. The wire connects or closes the safety circuit and allows the heater to continue with its call for heat routine. If you can identify the burnt wires, just hook them back up. Should be two, and are not polarity sensitive.
Thanks again for all of your help!

What initially appeared to be one fat wire was actually a pair of very thin shielded wires in a thick protective coating. When the transformer caught fire, it (presumably) melted away the shielding between the wires and closed the circuit. I cut out the burnt section, rewired, and everything is working perfectly!