Pool Heater Questions

mkgrady

Senior Member
Location
Massachusetts
I need to wire a propane pool heater. The heater electrical connection is 120 or 240. It requires a 15 amp circuit. The instructions say to never have the heater on without the pool pump running. It even implies that the pump should run for 5 minutes after the heater turns off.

I'm guessing most ignore the suggestion to make the pump run for a short while after the heater turns off. If not, what is a reasonable way to provide that control automatically?

There is a safety switch the instruction call a firemans switch that I have to provide. It interrupts the 24 volt control circuit. Is this just a typical single pole switch mounted in a bell box with an in use cover? Why is this called a firemans switch? Do I also need a service disconnect on the line voltage wires?
 

kwired

Electron manager
Location
NE Nebraska
I have pretty much no experience with pool heaters, but have worked on a few hot tubs before as well as other industrial processes with some similarities. Simple approach is a pressure switch or flow switch that proves there is water flow before allowing heating to happen, and would also interrupt heating should flow be lost. A little surprising the pool heater wouldn't have such a switch already incorporated into it.
 

ActionDave

Chief Moderator
Staff member
Location
Durango, CO, 10 h 20 min without traffic from wing
Occupation
Licensed Electrician
I have pretty much no experience with pool heaters, but have worked on a few hot tubs before as well as other industrial processes with some similarities. Simple approach is a pressure switch or flow switch that proves there is water flow before allowing heating to happen, and would also interrupt heating should flow be lost. A little surprising the pool heater wouldn't have such a switch already incorporated into it.
The pool heater has internal safetys to protect it. The thing with the fireman's switch is it interrupts the the heater control circuit prior to the time clock killing power to the pool pump just like a furnace t stat turning off the flame but the blower motor keeps running till the fire box cools down.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
I've done these two ways.

One is to use a "Fireman's Switch". The switch is just a micro switch that mounts in a predrilled location in an Intermatic timer. It does as described by others, it kills the low voltage circuit to the heater control 15-20 mins. before the pump shuts down.

The other, i just put the pump and heater on the same load terminal of the timer. That way it won't heat unless the pump is also running. I use this if the heater has a flow switch that prevents it from lighting/heating if there is no flow.

But if the mfg's specs say to use a "Fireman's Switch" then that's what I do. Some heaters have different heating chambers and don't require the heat to shut off before the pump, just at the same time. Others say that it will damage the heat chamber unless the pump runs for a while after the heater shuts off.
 

mkgrady

Senior Member
Location
Massachusetts
Thanks for responses. That clears up the firemans switch for me. I was thinking it was something different. Can the pump and the heater use the same circuit? There is only one circuit from the house to the pool. If the heater has to have a dedicated circuit I will need to have the yard dug up.
 

Dennis Alwon

Moderator
Staff member
Location
Chapel Hill, NC
Occupation
Retired Electrical Contractor
Thanks for responses. That clears up the firemans switch for me. I was thinking it was something different. Can the pump and the heater use the same circuit? There is only one circuit from the house to the pool. If the heater has to have a dedicated circuit I will need to have the yard dug up.


If it is just a control circuit then in all likelihood the pump and heater circuit can be together.
 

mkgrady

Senior Member
Location
Massachusetts
If it is just a control circuit then in all likelihood the pump and heater circuit can be together.

The circuit also powers a blower. It doesn't indicate what it draws. I would guess it's a pretty small load. Instructions just say 14 gauge wire and a 15 amp capacity. Says nothing about dedicated circuit or max over current protection. The pump is probably a 20 amp circuit.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
The circuit also powers a blower. It doesn't indicate what it draws. I would guess it's a pretty small load. Instructions just say 14 gauge wire and a 15 amp capacity. Says nothing about dedicated circuit or max over current protection. The pump is probably a 20 amp circuit.

If the pump is 240V then it's most likely around 7A, if 120V then 14A. Either way there is plenty for the heater and pump on same circuit as the heater may pull 2A at most. I connect these all the time with no problem.
 

kwired

Electron manager
Location
NE Nebraska
But if the mfg's specs say to use a "Fireman's Switch" then that's what I do. Some heaters have different heating chambers and don't require the heat to shut off before the pump, just at the same time. Others say that it will damage the heat chamber unless the pump runs for a while after the heater shuts off.
Power failure is going to shut them down together, I can see it may help make the heat exchanger last longer if it normally has water flow after shutting the heat down. Something tells me 10 - 15 secconds is plenty of time for water flow to cool the heat exchanger, though some have mentioned 10-15 minutes is what these controls typically have.
 

Little Bill

Moderator
Staff member
Location
Tennessee NEC:2017
Occupation
Electrician
Power failure is going to shut them down together, I can see it may help make the heat exchanger last longer if it normally has water flow after shutting the heat down. Something tells me 10 - 15 secconds is plenty of time for water flow to cool the heat exchanger, though some have mentioned 10-15 minutes is what these controls typically have.

All I know is the instructions/specs say to use a "fireman's switch". I don't know if they actually need the 15-20 mins. or they just know that's how much time the switch allows for.
The "fireman's switch" mounts in an Intermatic timer. It is just a micro switch and where it's placed (predrilled) allows the switch to open when the dial turns towards the "off" tripper, which is about 15-20 min. before hitting the "off" tripper. It is wired in series with the 24V control wire.

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