Hayward H200 millivolt.... clarification on operating procedures?


Well-known member
Jun 16, 2014
Uxbridge Ontario
We bought and installed a used Hayward H200 millivolt heater for our 21', 10,000 gallon above ground pool.

I need some clarification on its operating procedures but couldn't figure it out from the manual.
Am I supposed to leave the on/off switch in the on position and just turn down the thermostat when we don't need it?
Or should I turn the switch to the off position as well?

We do not have any automation, we usually run the pump at night on a timer but I am struggling with how to operate it now that we have the heater.

We don't intend to use the heater continuously, nor have the pump running all the time.
Would like to put the pump back on the timer, but obviously don't want it shutting off with the heater still running 😕

What is the cheapest way to handle this?

And where should that switch be on the heater? On all the time.... with the thermostat off.
Off when we are not using it... and then just run the pump and heater manually when we need it?
And then put the pump on the timer for night time running with out the heater?


TFP Expert
In The Industry
Jul 6, 2011
On a milivolt unit, once you light the pilot, it should stay lit all the time. Then you can use the on/off switch to turn it on and off. Thermostat can be in any spot you want. Usually you keep it at your desired temp setting. Then when you want to use the heater, flip the switch to on. As long as the pilot stays lit, you will be ready to use the heater. Just keep in mind that you're burning fuel all the time whether you use it or not.


Well-known member
Jun 16, 2014
Uxbridge Ontario

So, if I have the heater on set to temp, and the pump on a timer, would the heater not just turn itself on and off with the pump?
If I turn them both on together, and then the pump goes off, would it not detect the loss of flow and stop heating?
That should be some sort of safety feature right?

If so, does it work the other way too? If the heater is on and set to temp, and then the pump comes on, does it detect the flow and come on?

Or am I totally off base? Lol!


LifeTime Supporter
Aug 19, 2014
Pacific NW
if you get one of those intermatic timers with a fireman switch, it will shut off the heater
10-20 minutes before the pool pump shuts off, to provide adequate cooling / prevent knocking
in the heater.

If you heat manually, just make sure the pump runs an additional 5-10 minutes
after you turn the heater off.