Hayward H400 - sounds like it’s full of rocks!

[chiefwej]

I don’t use my spa/pool heater often. After all, Tucson has been over 100 degrees every day for weeks now. But today I turned it on. It fired up as normal, but after about a minute or so it sounded like someone was feeding gravel into it. It was so violent it was shaking the entire unit. I shut it down immediately, checked all valves and controls, before trying to start it again. Same result. Any experts out there with an option on this one?

 

[Poolbreh]

I would start with the thermal regulator. I had this happen with a mastertemp and thermal regulator had broken free. It sounded like gravel. I would take it out and test it.

 

[JamesW]

Sounds like boiling water.

Do you have an external bypass?

What is the pump speed?

What is the filter pressure?

Do you have pictures?

 

[chiefwej]

There is no external bypass. The spa pump (2hp single speed) the feeds the heater is on a separate loop from the pool filter. It is moving plenty of water, based on the spa jets. I don’t have a pressure or flow gauge on the spa loop.

 

[JamesW]

Does the spa pump have a filter?

If not, debris might be clogging the heater.

 

[JamesW]

Maybe the bypass or thermostat.

https://www.hayward-pool.com/assets/documents/pools/pdf/Parts%20Diagrams/H-Series.pdf

 

[JamesW]

https://images.inyopools.com/cloud/documents/hayward-heaters-h-series-low-nox.pdf

 

[JamesW]

Below, you can see the spring loaded internal bypass.

Maybe the bypass is open allowing to much water to bypass the heat exchanger.


Maybe the thermal regulator is stuck closed, which will block flow from exiting the heat exchanger.

 

[JamesW]

If the water is overheating, the high limits should be opening and preventing the water temperature from getting to the boiling point.

Check the high limits to see if they are working correctly.

I would plan on changing the thermal regulator and the high limits at minimum and the internal bypass if necessary.

 

[chiefwej]

If the water is overheating, the high limits should be opening and preventing the water temperature from getting to the boiling point.

Check the high limits to see if they are working correctly.

I would plan on changing the thermal regulator and the high limits at minimum and the internal bypass if necessary.

I think the high limit is working, the burner shut down before I cut the power to the heater. Based on everyone’s help, I’m pretty sure it’s the bypass valve, but the thermostat should also be replaced. Too bad this looks like a real PITA job to do. Lots to disconnect to move the heater, including hard pipe gas line and cutting and reconnecting PVC. Might just farm this one out. Thanks all.

 

[JamesW]

You should be able to remove the header without cutting pipe or touching the gas line.

Undo the unions and remove the header nuts and the header should pull off if you have enough flex in the pipes to move them back about 2".

The header only needs to clear the studs and the pipes should be able to be shifted out of the way enough to get the header off.

 

[JamesW]

The gas line has a union you can open if you need to shift the heater a little bit to get the header off.

Just close the gas valve and open the union.

 

[chiefwej]

Based on all the support from you TFP folks (well, that and none of the local pool services wanted to tackle the repair) I’ve decided to just DIY. Everyone wanted to give me a quote on replacing a 15+ year old heater, but no one wants to repair one. So, I researched and ordered the parts. I’ve disassembled the unit, but it looks like it will be much harder to reassemble it. All the nuts that are along the bottom of the manifold were very difficult to get off without dropping and losing them. How to get them started and back on, will be a real challenge. Since they are made of a high grade stainless steel, they are non magnetic, so that doesn’t help. Once the manifold is back in place, I have limited access, and getting the nuts back on where I can’t see and can barely reach, without cross threading or dropping any of them will be difficult.

 

[JamesW]

A nut catch long socket with 9.5 mm insert angle with a mechanism that stops bolts and nuts from falling out.

 

[JamesW]

 

[JamesW]

You can put some putty in the socket so that it sticks to the nut and keeps it from falling out.

Pack some sticky putty into the socket with enough room left for the nut and the sticky putty will hold the nut until it gets started.

Any sticky putty will work like butyl tape etc.

 

[chiefwej]

I’ll try that trick to keep my nuts in place.

 

[JamesW]

I’ve disassembled the unit

Were you able to see any defective parts?

 

[chiefwej]

Were you able to see any defective parts?

 

[chiefwej]

Repaired and back in service. I found out why local pool service didn’t want this job. It was a PITA, right to the end. Even what I thought wouldn’t be a problem (reconnecting the supply and discharge unions) seemed to take forever. Just couldn’t get them to line up without cross threading. Thanks again for all your support.