Wiring up a new gas heater.

another one

Well-known member
Jul 1, 2010
Seattle area, WA
Okay, I'm replacing my Pentair Minimax with a Pentair MasterTemp tomorrow. The pool guy's quote didn't include any gas work - and we needed the gas line extended and all new venting as the MasterTemp requires Z-flex while the MiniMax uses B-vent. And the pool guys quote was about $1500 more than what I could get the heater for online. :(

So, I have the person who installed my boilers coming over tomorrow - he claims he installed the pool heater too. But he is only doing the gas and venting, not the electrical or the plumbing.

Now the pumbing is very straight forward, so I'm not worried about that, but the electrical has me a bit perplexed - and yes, I've wired houses from installing a panel outward, so I'm comfortable do this work.

We have a Jandy Aqualink with the Jandy power center.

Here's what I have - low voltage - just a pair of wires off a relay that closes when pool heat is wanted. MasterTemp instructions explain where these go.

High voltage:
Five wires going to the heater - 2 black, 1 red, 1 white (neutral), and one green (ground). One of the black and the white wires go to the control center to a breaker labeled "heater fan" and are on all the time, 120 volts, (unless you turn that breaker off). Note: The MiniMax had a power vent installed and these 120 volt wires went to the power vent control.

The other black and red are wired to my pool pump and generate 240 volts when ever the pool pump is running and they are on the same breaker as the pool pump.

And the black / red pair off the pump went to the pool heater controller (really the 24 volt transformer). So the transformer was only powered when the pump was running.

The MasterTemp can run off of 240 or 120 volts.

So the question is: which set of wires (240 volts powered with pump or 120 volts always on) do I use and why?

Thanks for reading such a complicated post.

The MasterTemp manual is here: http://www.pentairpool.com/pdfs/MasterTempOM.pdf

Bama Rambler

Mod Squad
TFP Expert
Bronze Supporter
LifeTime Supporter
Jun 22, 2009
SouthWest Alabama
You got it right. You never want the heater on if the pump isn't running. There are safety cutouts in the heater but you don't want to use them as standard operating limits.

another one

Well-known member
Jul 1, 2010
Seattle area, WA
Thanks. All complete and running - or it would be running, but we're still slowly draining the pool, but hopefully this weekend it will be all ready to swim in.