Heater and Pump Flow

[ssanto]

I've got a new pool and spa. It has a Hayward 500 BTU heater running on propane. The pump is a Tristar VS 950 omni variable speed pump. To keep the noise down, I usually run it around 70-80%.

Today we started up the heater with the pump running at 80%. It worked fine for about 10 minutes then it started popping and rattling and eventually shut off with code HS. I understand that this happened because the heater wasn't getting enough flow and water inside of started to boil. I ran the heater at 85% and it worked for a while. Then when I slowed it back down to 80% the popping started and the heater shut down. This is with the valves configured to "spa mode" where it is just circulating water through the spa.

Then I tried it in "pool mode" where it is circulating water through the pool. It ran fine with the pump as low as 70% and didn't do the boiling water thing.

So I suppose the spa has more restriction in the water flow than the pool and the pump has less GPM at the same RPM.

Question - Should I expect to be able to have enough flow through my heater with that Tristar 950 pump running at only 80%? The heater manual says it requires 40 GPM. I don't know if something is wrong with my setup or if this is just how it is supposed to work.


Thanks,
Sal

 

[ajw22]

Welcome to TFP Sal.

Please post pics of your equipment pad and create your signature with details of your pool and equipment so we can understand your entire pool system.

What model filter do you have and what is your filter PSI?

When was the last time you cleaned your filter?

A clogged filter can cause low water flow.

 

[ssanto]

The pool is new so the filter has only been run for a couple months. I'll check to see if it is dirty/clogged. I don't trust the pressure gauge on the filter since it always reads the same regardless of whether the pump is on/off.

Thanks!

 

[ajw22]

You should get the pressure gauge replaced under warranty from your pool builder. It is a key tool to know what is happening with your filter.

 

[ssanto]

Thanks!

We found out what the problem was... the valves were set to allow water to bypass the heater so it wasn't getting 100% of the flow from the pump. Doh!