GuardDog LWCO Failing?

nz

Hello,

Semi-competent homeowner here. Second heating season at our new house. House has a Weil-McLain LBG-6 hot water boiler, four zones.

I just turned on the boiler to test it since it's getting cooler out, and the LWCO (GuardDog McDonnell & Miller brand) is stating that there is low water (red light) in addition to the normal green light. Obviously the boiler is not heating, which is understandable. 

I don't believe the boiler is low on water, but as I'm newer to hot water I'm not sure how to check (no sight glass like steam). I did pull some water out of the expansion tank (old steel one above in the ceiling), and the gauge is reading 15-16psi so I think there's plenty of water in the system.

Do you think the LWCO has failed or does it need cleaning? I checked the manual and it looks like it needs to be cleaned every 5 years or so.

JUGHNE

The LWCO probe may need cleaning.

Hopefully you can isolate the boiler from the zone systems to drain it down.

Use no Teflon tape when re-installing.

Make sure all ground connections are good.

leonz

I have the RB-122-E low water cut off with the immersed sensor tab.

My RB-122-E has only one Light Emitting Diode and it is going to show either red for low water condition and shut down the boiler or green for adequate water in the boiler not both.

If you have the single LED and it shows both red and green it is best to call Bell and Gossett or a Bell and Gossett distributor and describe what it is doing and proceed from there.

If the Low Water Cut Off is in the side of the boiler it located in the steam jacket and the boiler needs to be drained down and the Low Water Cut Off removed and the conductive tab cleaned with hydrogen peroxide or finger scrubbed with hot water and dawn dish soap.

It is best to have a steam qualified plumber come and service the boiler as the burners may also need cleaning.

You just need a good steam plumber to come by and look at your boiler, clean it and check the Low Water Cut Off for you.

nz

Thanks for the suggestions guys. I isolated all four zones and drained off the boiler, cleaned the probe, put all back together and it's on!

I'm still going to have to bleed off some of these zones I think, there's no way to purge the air above the boiler other than the old steel compression tank didn't give me a lot of air back.

neilc

post a distant picture or 2 of the boiler, circ, and tank, shown all in one,
if it's piped and pumped correct that old tank should pick up small air,
have you bled the tank down to re establish its air cushion?

nz

neilc said:

post a distant picture or 2 of the boiler, circ, and tank, shown all in one, if it's piped and pumped correct that old tank should pick up small air, have you bled the tank down to re establish its air cushion?

Thanks NeilC. I did bleed the tank down but I'm not sure how much is the "right" amount. Boiler manual doesn't specify.

Here are some photos of the boiler and the piping. I did buy Dan's book and read it last Winter, I'm aware the circulators are in the wrong spot

HomerJSmith

I think that the GuardDog is mounted in the wrong place. The black tip is suppose to rotate and clean the probe and is supposed to be in the flow so that it spins. Clean the probe with CLR. Deposits may interfere with the conductance or capacitance, I forget.

leonz

Is that a before picture of the low water cut off????

I hope it is as there should be nothing like tape or
liquid sealer on the threads of the low water cut off.

I am surprised that the plumber installed the low water
cut off the way they did.

As the s team chest tapping is larger they should have
threaded in a reducing bushing rather than a pipe nipple
and reducing bell.

EBEBRATT-Ed

Somebody did a nice job there probably in the 60s on the piping

nz

leonz said:

Is that a before picture of the low water cut off????
I hope it is as there should be nothing like tape or
liquid sealer on the threads of the low water cut off.

I am surprised that the plumber installed the low water
cut off the way they did.

As the s team chest tapping is larger they should have
threaded in a reducing bushing rather than a pipe nipple
and reducing bell.

That's after - I only took it off and put it back on. There's no teflon tape, only blue pipe thread sealant.

I downloaded the boiler manual - that's an "approved" location for a LWCO for hot water, but after reading your comments I agree it's a less than ideal location. From what I can tell from reading the LWCO manual, I would have to do some significant re-piping to move it.