I need help troubleshooting gas heater

[abfab]

We have had a bunch of issues with our pool this year including a hole in the liner, skimmer valve leak and a faulty limiter in the swg. The latest are our heater and pump.

Our heater was working fine when we tested on opening. When we used it for the first time it ignited fine and seemed to be heating ok for a while. Later in the day I noticed the water was cool and when I checked the heater it was no longer running. The pilot was on however.

Here's what I have done thus far:
- Jumped the TH/PP-TH terminals. Doing so will ignite the heater.
- Got 330 mv with these terminals (no jumper cable attached). I don't have much experience with a multimeter so hopefully I did it correctly. This seems low from what I've read but I don't know what is normal for this heater.
- Tested the pressure switch for continuity and it has it.
- Tested another part that has two white wires. Can't tell from manual what its called - possibly high limit switch or fusible link. It had continuity.
- Switched filter to recirculate to test if it was a low pressure issue. This made no difference. I backwashed the day before the problem started and my psi reading is normal.

What are my next steps?

Also, this may be an unrelated issue, but my pump shuts down after about 5-10 minutes on high. I have it running on low 24/7 with no problems. This started when I had a skimmer valve air leak that was causing the pump to lose prime. A few times the pump got dry and very hot before I noticed the problem. I suspect that may have damaged the pump. The valve was fixed but this pump problem remains. I don't think its related to the heater issue but am mentioning it just in case. Fortunately it runs long enough that I can run tests on the heater (eg jumping terminals).

 

[ps0303]

A strong pilot and pilot generator would produce at least around 400+ mv, I like at least 450mv, in order to operate the system. Your reading of 330 is way low. Sounds like a failing pilot assembly, if it doesn't have a strong blue flame, or the the thermopile is bad.

How is the overall condition of the unit? Meaning it's not rusting away or anything is it? Just wanting to see if maybe you might want to upgrade it to something newer.

 

[abfab]

It seems to be ok condition from what I can see. I don't have thermopile listed in the manual. Is that the same as the pilot generator or pilot electrode?

 

[ps0303]

Wait, you have the LG correct?

Yes pilot generator.

 

[abfab]

yes - lg. I have to check but I think we replaced it a couple of years ago. Is it common for them to have such a short life?

 

[ps0303]

Yes it's possible but they should last longer than a couple of years.

 

[abfab]

I replaced the pilot generator and am now getting 450mv however it did not fix the problem. I jumped the pressure switch connectors and it ignited, so it appears to be faulty. What I don't understand however is why? It has continuity. From what I had read I understood that getting continuity means that it is working. Is it possible for it to be faulty but still have continuity?

I took it off and made sure there was no rust where the connectors attach (the wire connectors were replaced in the spring) and that there was no blockage where the siphon loop connects. I also retested with the filter on recirculate to again confirm that its not a low flow issue.

Before I buy a new pressure switch is there something else I should be testing or is this definitely the faulty part?

 

[danpik]

How are you confirming continuity? If you have not done so already, test it one of two ways with a Volt/Ohm meter.
First way is to unhook both wires and with the pump off, check for continuity on the Ohm scale. With the pump off you should read OPEN. With the pump ON you should read closed. The closed reading will be the same as when you touch both probes on the meter together.

The other method is to set the meter to volts, AC and check both sides of the switch to ground (chassis). This is with both wires connected. With the pump on, you should see voltage on both sides of the switch and with it off only on one side.

check each switch in the system this way

 

[robhdrider]

In your first post you mentioned that you have to run your pump on low all of the time and possible pump damage. Are you sure you have adequate pump flow to satisfy the heaters pressure switch? These would seem to be closely related to me.

 

[abfab]

Ok, here is the latest... I used the first method of testing (I don't know what chassis ground means). Assuming that I did it correctly, with the pump off both the fusible link and pressure switch read open. With the pump on the fusible link reads closed, but I was getting a reading for the pressure switch. The reading varies every time I touch with the probes but its not close to zero. What does this mean?

There are also two high limit switches (135/150 degrees) that I haven't tested as they are not easy to access.

Yesterday my FIL was able to get the heater working. A short time later (maybe 5-10 minutes) I noticed that the pump had shut off. He said that he fixed it by adjusting the bolt connected to the siphon tube. I don't quite understand his explanation, but he said that he noticed earlier in the season that a small amount of water was leaking so he tightened it. According to him he theorized that doing this caused too much (or too little) air thus causing the pressure switch to malfunction. After he left I restarted the pump but the heater is back to not working again. Still nothing today. Whatever he did seemed to temporarily fix it, but I don't know why.

Today I was able to run the pump on high for 2+ hours without shutting down. I then switched it back to low. I did not have the heater on. This suggests to me that the heater is causing the pump to shut off. What would cause this?

robhdrider: My pump must be switched to high for the heater to work. It will not operate if its on low.

What are my next steps??

 

[danpik]

Sounds like your pressure switch is not closing properly. Some of these can be adjusted, some can't.

BTW, Chassis ground is simply any bare metal on the heater chassis or frame. This will give you a zero volt reference for your meter when checking voltages. All voltages in the safety loop are ~24 volts

 

[ps0303]

The heater can't cause the pump to shut down. There is nothing that I am aware of that could cause this or be setup to cause this action.

 

[abfab]

Thanks for all your help. I replaced the pressure switch and its working!!