H150 Little heat

[eze426]

Hello all. This is my first post and I wouldn't be posting if I knew the answer. I have a Hayward H150 (H1501) millivolt pool heater. It turns on and ignites just fine. The issue is there's next to no heat going into the pool.
We first bought the house in 2020 and had a guy open the pool for us and get the heater working. The heater used to put out enough heat, you could feel it on the otherside of the pool. It no longer does that. It's barely a few degrees warmer. Does it have something to do with the bypass and thermostat on the heat exchanger? Thanks in advance.

 

[PoolGate]

Can you measure the exhaust gas temperature? One of those infrared handheld thermometers work great for this. Also can you post a pic of your plumbing?

 

[ajw22]

Welcome to TFP.

The heater puts out a fixed amount of BTUs. The heat is either going into the water or out the exhaust.

What is your exhaust temperature?



Post pictures of your "bypass".

There is no thermostat on the heat exchanger. When the water is at the setpoint temperature the thermostat shuts off the heater.

 

[1poolman1]

Hello all. This is my first post and I wouldn't be posting if I knew the answer. I have a Hayward H150 (H1501) millivolt pool heater. It turns on and ignites just fine. The issue is there's next to no heat going into the pool.
We first bought the house in 2020 and had a guy open the pool for us and get the heater working. The heater used to put out enough heat, you could feel it on the otherside of the pool. It no longer does that. It's barely a few degrees warmer. Does it have something to do with the bypass and thermostat on the heat exchanger? Thanks in advance.

If the heater is firing it is heating the water. It could be how much of the heater is firing.
It may be that some of the burner orifices have been clogged with spider nests. They love to block them and the heater should be fired at least once a month for a few minutes to chase them away.
That is a very tiny heater and only has 3 burners. With only one orifice blocked, you could have an output reduction of 33% . That would limit your heating output capacity to about 80K BTU. That's not a lot of heat for a pool of any size. You could have 2 clogged and only the burner at the pilot lighting. Now you're down to about 40K BTU into the pool.