Pentair 300k BTU Pool Heater - Service Heater Light

[JackDaniels07]

Hi all,

About six years ago I purchased a home with an inground swimming pool. Since this was my first time owning a pool I searched the internet in an effort to learn all I could. Luckily I stumbled up TFP and have been able to address any issues I've had just by searching the boards. After six years of lurking, I've run into a problem that I think requires a post. Hopefully, someone here can point me in the right direction.

I have a natural gas Pentair 300k BTU (Model #460734) installed. Today I opened my pool for the season and the heater failed to start and the service heater light was on. I gave it a few more attempts with no joy. After a look at the owner's manual, I was able to find that the AFS light was on. I also pulled off the cover to the ignition module and found that a critter had made a nice home inside! Once I pulled out the little nest it made I saw a few wires had been chewed (see picture). I checked the remainder of the unit and it appears the only wires that were damaged are the ones in the photo.

My question is would it be possible to replace just those damaged wires? In addition, could that be causing the AFS light to go off?

Thanks for any help you can offer. If any additional information would help let me know. I plan to take another good look at the heater tomorrow!

 

[ajw22]

AFS is the air flow switch that senses if the blower is on and there is sufficient air flow to the burner.

Does the blower run when the heater starts?

The AFS is a white tube running up to the switch that you can gently blow into to test.

That rat made a mess with the chewed wires and also urine all over the ground connections that can give you flame sensing problems. You are likely to have multiple problems to fix to get the heater running. Some reading...

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

Heater Flame Sensing - Further Reading

www.troublefreepool.com

Products | MK Rat Proofing

 

[JackDaniels07]

AFS is the air flow switch that senses if the blower is on and there is sufficient air flow to the burner.

Does the blower run when the heater starts?

The AFS is a white tube running up to the switch that you can gently blow into to test.

That rat made a mess with the chewed wires and also urine all over the ground connections that can give you flame sensing problems. You are likely to have multiple problems to fix to get the heater running. Some reading...

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

Heater Flame Sensing - Further Reading

www.troublefreepool.com

Products | MK Rat Proofing

Thanks for the reply ajw22, I appreciate all the resources. I wish I knew about the rodent prevention kit! Knowing what I know now it's worth it. I'll be placing an order for that immediately. I'm reading through the links you posted and I'll begin the process to figure out what the issue is. I plan to post an update.

Jack

 

[JackDaniels07]

AFS is the air flow switch that senses if the blower is on and there is sufficient air flow to the burner.

Does the blower run when the heater starts?

The AFS is a white tube running up to the switch that you can gently blow into to test.

That rat made a mess with the chewed wires and also urine all over the ground connections that can give you flame sensing problems. You are likely to have multiple problems to fix to get the heater running. Some reading...

Pentair MasterTemp Heaters - Further Reading

www.troublefreepool.com

Heater Flame Sensing - Further Reading

www.troublefreepool.com

Products | MK Rat Proofing

Ok, I pulled the unit apart and located the white tube you referenced. I blew slightly into the tube and heard a clicking(?) noise. It sounded like something switched but the blower did not come on. I can feel the motor getting warm though.

 

[ajw22]

AFS does not turn on the blower. Sequence is blower motor should turn on, AFS senses air flow, and switch closes to start ignition sequence.

Rat probably chewed up wire powering blower motor. Can you turn blower by hand? Motor could be seized.

 

[ajw22]

Mastertemp 400 humming (already replaced the "run" cap) still humming

Hi my tfp friends I have a Mastertemp 400 and its blower humm when pool or spa are turned on (humms like a pump motor with a failed cap), and "service heater" led turns on, i already replaced the cap (8uF-250vac), but still the same failure. Problem starts when working (last weekeend) there...

www.troublefreepool.com

Here is a thread about the blower operation and testing.

Also..

Sta Rite sr200 lights and runs then stops

Hi all, thanks in advance for any help or advice you can provide. I have a sta rite sr200 “MAX-E-Therm” that is driving me nuts. Short version: heater turns on and fires up but stops after 5 sec and shows an AFS error. It has been working consistently since we bought the house about 1.5 years...

www.troublefreepool.com

 

[JackDaniels07]

AFS does not turn on the blower. Sequence is blower motor should turn on, AFS senses air flow, and switch closes to start ignition sequence.

Rat probably chewed up wire powering blower motor. Can you turn blower by hand? Motor could be seized.

Update:

I went back out and removed the cover to the blower motor and used a screwdriver to manually turn it. I felt some slight resistance and heard some crunching noises and then it spun freely. Plugged the heater back in and it started right up. It appeared some debris - looked like acorns came out. The heater has now been running for the last 10 minutes without issue however I am still hearing a slight rattle which I think is debris still in the fan enclosure. I couldn't upload a video so instead, I threw it up on GOOGLE Drive - here is the link: Pool Video - Google Drive. You'll see the wires have been taped up which I did so I could troubleshoot the bigger problem. I'll be replacing the damaged ones ASAP. I've ordered the MK rodent kit as well.

Any idea what gauge the wire is?

Thanks, ajw22! It's at least running!

 

[JackDaniels07]

I am having a similar problem (minus the rodents) It seems like you're the expert on heaters.

Mine is clicking but no ignition and no blower. I am not sure gas is getting into the heater - would this happen if gas wasn't getting in? (maybe bad regulator at tank or something)

Henry,

The links posted by ajw22 have loads of information. I just started at the beginning to try and isolate the problem. Good luck.

 

[ajw22]

@JamesW you know what gauge wire is used in the heater?

 

[JamesW]

Control wire is 18 AWG. Line voltage is 14 AWG.

The wire type should be printed on the wires.

If any of the original wiring supplied with this heater must be replaced, installer must supply (No. 18 AWG, 600V, 105° C. U.L. approved AWM low energy stranded) copper wire or it’s equivalent.

Line voltage field wiring should be 14 gauge, with a circuit capacity of 15 Amps.

 

[JackDaniels07]

Control wire is 18 AWG. Line voltage is 14 AWG.

The wire type should be printed on the wires.

Thanks, JamesW. I'll grab some replacement wires and fix the chewed ones.