LWCO Electric Issues?

distance22

Hi,

I have a PSE802-U-24 LWCO where the red light is flickering on and off randomly even when boiler isn't running. It is almost like there is a short of some sort. The weird thing is that the LWCO works, when I test it and let water out, it turns the burner off. I had an HVAC pro come out and he recommended replacement. I replaced the entire unit (probe and electronics) with a brand new unit but it is still doing it. I checked all the electrical connections because I was thinking maybe there was some sort of short, but they all have tight wire nuts.

The boiler has a dedicated circuit coming out of the main electrical panel into a 24v transformer by the main panel. Whoever installed it then ran low voltage wire across the basement to the junction box on the boiler. The low voltage wire has two wires coming out of it - red and white. I measure the voltage across both and it measures 28v. From the junction box one of the wires goes to a switch and then the other all the controls.

Has anyone ever seen this before? I find it odd because the LWCO is still working as well. I am most likely going to call am HVAC pro but wondering if anyone else has any ideas first.

Video -
https://youtu.be/bwWiV-k4RQI

Jamie Hall

My first thought with that wiring setup is... bad grounding. Is the boiler solidly grounded back to the main switchboard ground?

EBEBRATT-Ed

I agree with @Jamie Hall the low water cut off probe sends a small electrical current through the boiler water. It's possible the boiler is not grounded , although if city water is piped to the boiler this is unlikely. Using whatever wire you have kicking around run a wire from the green ground screw in the low water cutoff back to your ground wire coming out of you electrical panel (it's usually a bare wire) that either goes to a ground rod or to the metal water pipe.

Just run it across the floor to try it, if it works you can have a permanent equipment ground wire installed.

HVACNUT

Did you also replace or at least remove and clean the well? And no tephlon tape on the threads. Compound only.

distance22

Good ideas. I’ll try running a ground wire to see if that is it. As far as the installation of the LWCO, yes I only used a minimal amount of pipe dope, no tape.

What do you mean by clean the well @HVACNUT ? Clean the boiler? I did do a full flush and used Scout boiler cleaner to get all the junk out. I’m also going to skim again once it runs more regularly.

HVACNUT

I'm sorry, not the well, but the sensor. If you replaced it then ok. If not, the probe tends to get dirty and cleaning it helps.

distance22

Update: It is now fixed.

Tried running ground wire and it didn’t solve it.

I went to skim/flush again since it has been running a few weeks. I took apart the pigtail and cleaned all the piping around pressure gauge/pressuretrol. I had to unwire the pressuretrol to take it off. It was very oily and black. Flushed it and then skimmed it. It now works perfectly with no dimming light. I’m thinking maybe it was so gunky it was causing a bad reading even though the LWCO and probe is brand new. Or maybe there was bad contact on pressuretrol wires and that fixed it when I reconnected? Either way glad it is working!

D107

Glad you've solved your issue. I'd just throw in another question in to the Wallies on this: Can lack of water conductivity be a cause of this kind of thing?

mattmia2

The more stuff that is dissolved in the water, the more conductive it will be. What may happen is it becomes so conductive it becomes an error condition making it think the probe is shorted.

Jamie Hall

D107 said:

Glad you've solved your issue. I'd just throw in another question in to the Wallies on this: Can lack of water conductivity be a cause of this kind of thing?

It would have to be incredibly pure water. 10 minutes in pretty much anything except glass or polyethylene and even ultrapure distilled will conduct just fine.