Gas Heater Caught Fire - Rings Were Not Connected?

[Aquatica]

we moved a gas heater to another location and hooked it back up. Apparently we didn't hook some "rings" up and gas leaked and the unit caught fire.

This is what the gas guys said. However I only remember us disconnecting a gas line and the in and out water lines. Is there something else we missed? like these rings? (which we never disconnected).

Thanks for any insight!

also this heater was off during the summer. when we started it back up it started making some knocking noises. like tennis shoes in a dryer. so we cut it off and called another pool company. they opened it up and looked at it. didn't touch it but it started working again ok. weird!

could this knocking be related to these "rings"?

 

[PoolGuyNJ]

Given your geo, without picture of the gas line connection, I am having a hard time understanding what the gas guys meant. We don't use compression rings on gas pipe. O-rings and gas connections would be a definite no no since they age and crack/split. Telfon sealant paste, aka pipe dope, should be used with threaded connections.

The banging is likely a result of a lack of water flow through the heat exchanger. When the heater fires, the lack of flow causes what water there is in the tubes to boil. The pressure switch should have detected that, assuming it wasn't shorted/disabled. The cause of the low flow could be the result of several conditons:

1) Calcium build up in the heat exchanger tubes
2) The internal flow bypass was stuck open, preventing sufficient flow into the heat exchanger
3) A failed temperature regulator.

None of these 3 conditions should cause a fire.

The failure to use pipe dope on the threaded connections could as gas is then able to leak. The results could be explosive.

Clogged burners could cause a back fire. This would take a while to become explosive but many heaters have fusible links that melt when exposed to flames in the front. When the link melts the regulator shuts the supply and the fire goes out.

Scott

 

[Aquatica]

Given your geo, without picture of the gas line connection, I am having a hard time understanding what the gas guys meant. We don't use compression rings on gas pipe. O-rings and gas connections would be a definite no no since they age and crack/split. Telfon sealant paste, aka pipe dope, should be used with threaded connections.

The banging is likely a result of a lack of water flow through the heat exchanger. When the heater fires, the lack of flow causes what water there is in the tubes to boil. The pressure switch should have detected that, assuming it wasn't shorted/disabled. The cause of the low flow could be the result of several conditons:

1) Calcium build up in the heat exchanger tubes
2) The internal flow bypass was stuck open, preventing sufficient flow into the heat exchanger
3) A failed temperature regulator.

None of these 3 conditions should cause a fire.

The failure to use pipe dope on the threaded connections could as gas is then able to leak. The results could be explosive.

Clogged burners could cause a back fire. This would take a while to become explosive but many heaters have fusible links that melt when exposed to flames in the front. When the link melts the regulator shuts the supply and the fire goes out.

Scott

Thanks Scott. Don't know whats going on with this heater but CH was at 450 in the pool it was in. However it was much higher when I took the pool over so could be scale inside. As for the fire it could be a bad gas line hookup. Won't be touching gas heaters again! Don't need them down here and we just put in heat pumps anyway.

The gas heater that burnt up was going to be dumped by my subcontractor as we installed a heatpro. client has two houses and wanted us to move the old gas heater to the next house (which has a gas heater of its own already). so we are now going to put the old one that's still working back. This time we are getting a gas guy to hook up the gas line and electrics and we will just deal with the plumbing.

Down here it takes two companies to install a gas heater. lol! The gas people don't do plumbing and the pool people don't do gas. Anyway its a learning experience. Once client is happy all will be well.