Auto Water Feeder won't turn off

acab1975 · March 2020

1-pipe steam, Dunkirk PSb-50 boiler, McDonnell Low Water Cut-off, Safgard auto feeder. I'm not the original owner/installer of this system.

About 3 times in the past two years, it has happened that the auto-feeder turns on during a heat cycle, calling for water when none is needed, and not stopping on its own. I have remedied this in the past by, shutting off water to autofeeder, draining the boiler, removing the probe (a one-piece brass & fiberglass deal), cleaning the crud off of it, reinstalling it and it doesn't turn back on.

Today, it happened again, so I did my usual cleaning (probe wasn't that dirty since this last happened about a month ago), but the auto-feeder valve is still open, sending water to the boiler and overfilling it. I have the water shut off to the auto-feeder for now. Boiler will still cycle on when thermostat calls for heat. Note that water isn't very dirty when I drained it.

The entire system is quite old. I'm wondering if anyone has any quick tips or advice. Thank you.

jhrost · March 2020

Seems like you are going to a lot of trouble draining the boiler, as well as adding a lot of fresh makeup water which they warn against on this site continuously. I would just leave the automatic feeder valved off if it was me. I think I would also try skimming the boiler once if you haven't done it yet, which may get rid of some of the contaminants that may still hang around after a boiler draining. This wouldn't cost you anything except for the water. If the water really looks clean as you say and the probe does also, you might want to invest in a new probe?

Also if I had my choice I think I would go with the Hydrolevel Vxt feeder and put a big time delay on the time to feed to possibly avoid the nuisance you are talking about. I have a Dunkirk boiler also with the side outlets and it has a tendency to kick on after the thermostat actually shuts down the burner because the water tends to be slow to return, but then just ends up pointlessly overfilling it.

I suppose it is also possible that if the water line tilts somewhat that the sight glass may give a different picture than what the probe is actually sensing in the part of the boiler where it lives?

Fred · March 2020

While the probe may be clean, it may be faulty. Either that or you have an intermittent short in the wiring between the Low Water Cut-off and the auto feeder, a bad control board in the LWCO or the solenoid in the feeder is faulty. Time to do some testing. You will want to leave the feeder off until you find the problem. You've been lucky the last three times. You don't want to come home and find the system has filled to a point where water is spilling out of radiator vents and ruin floors, ceilings etc. It happens more often than you might think.

acab1975 · March 2020

Fred said:
You don't want to come home and find the system has filled to a point where water is spilling out of radiator vents and ruin floors, ceilings etc. It happens more often than you might think.

I never considered that, but wow, that would've been an awful outcome. I'll get it sorted and report back with the resolution.

ethicalpaul · March 2020

I'll mention it because I don't think anyone else has. A point of failure can be the solenoid valve itself getting stuck open.

acab1975 · March 2020

ethicalpaul said:
I'll mention it because I don't think anyone else has. A point of failure can be the solenoid valve itself getting stuck open.

inside the auto-feeder, you mean?

Fred · March 2020

Yes,
It's inside the feeder.

acab1975 · March 2020

Here are pictures of the LWCO and auto-feeder. The auto-feeder is so old that I cannot find any images online that look similar, though that model number is still out there as an updated model. The LWCO lights appear to be permanently off. The probe I unfortunately didn't take a photo when it was out, but it looks like this: https://parts4heating.com/v/vspfiles/photos/100277756-2T.jpg

Don't mind the pressure gauge, I know it's wrong. The last idiot installed it.

ethicalpaul · March 2020

Your probe looks the same age (and model) as mine (maybe 80s to early 90s?), and your feeder looks even older with that mod 60s font.

If it were me, I'd replace the feeder with a VXT with digital counter on it--that will be transferable to your next boiler.

My opinion of the probe is it has very few parts that can fail (but they can!).

Have you done a test where you raise and lower the water level a few times to see if the LWCO properly lights up and then turns off after it fills? Your thermostat probably needs to be calling for heat during the test so the LWCO gets power.

In doing that, you might even catch it in failure mode where you can tell where the failure is. If the lights are working the failure is probably in the valve.

acab1975 · March 2020

ethicalpaul said:
Have you done a test where you raise and lower the water level a few times to see if the LWCO properly lights up and then turns off after it fills? Your thermostat probably needs to be calling for heat during the test so the LWCO gets power.

In doing that, you might even catch it in failure mode where you can tell where the failure is. If the lights are working the failure is probably in the valve.

I didn't do this test. The LWCO lights don't work at all...probably reason enough to replace it.

ethicalpaul · March 2020

So they don't even work if the thermostat is calling for heat? In that case I guess I would replace both units now. As others said, it's a small price to pay compared to flooded wood floors.

acab1975 · March 2020

Does one even really need an auto-feeder if the LWCO is in good working order? I'd imagine that if replacing the LWCO and probe doesn't remedy the issue with the auto-feeder not turning off, I could just rely on the LWCO to shut down the boiler when it senses a low water level condition, and that I then go down and manually fill the boiler. For me, preventing a dry-firing of the boiler is the must-have, whereas automatically filling the boiler is a nice to have. I'm down there and checking water gauge pretty often anyway.

Fred · March 2020

I do not have a feeder on my boiler. Many of us don't. It is nice to have but we often suggest that manually adding water is a better option. It causes a homeowner to pay a little more attention to their boiler and it significantly decreases the risk of a stuck feeder in the open position, causing flooding.

ethicalpaul · March 2020

I'm very torn on it. Having an automatically filling boiler is nice to have, until you go away for a week in the dead of winter forgetting to check the water level and the boiler shuts off and your pipes freeze. Then it's a must-have.

acab1975 · March 2020

Maybe the thing to do is keep a functioning auto-feeder, but only turn the water on to it when going on vacation, and leaving it shut off otherwise.

JUGHNE · March 2020

With your LWCO acting up as such, you want to be sure that it does shut the fire off as the level drops. You can manually test by draining while firing.

Shut off the water supply first of course.

Then refill manually.

jhrost · March 2020

I've got that type of low water cutoff and for over a decade I've never cleaned the probe and it still works fine. According to the info that came with it though , it is supposed to be self-cleaning , reducing probe maintenance to every five years. It mentions lime buildup as the main problem. My thinking is that I skim a few times every year, and did a flush and wanding a few years back - so maybe that is helping to keep it clean. So if it ain't broke don't maintain it. That may not be smart though, it may be hard to get the thing out if you wait too long, but boilers don't last too long nowadays anyway apparently.

Gordo · March 2020

@acab1975 : As others have mentioned, it's of vital importance to get your LWCO working properly. It is a safety control and so must work. So, I'd replace that McDonnell Miller very soon, even if it seems to be working, and that includes replacing the probe, too.
The feeder can be rebuilt, or replaced or abandoned... your call on that one.
Below is a short video of the VXT-24 (second generation) that you appear to have. I'd skip ahead to time index 2:48 to bypass the boring stuff....

https://www.youtube.com/watch?v=xoSlNjBlCh4

exqheat · March 2020

Your attitude is penny wise and a pound foolish. Both devices have their benefits. Having both in good working order will save you in the long run. What sense is it to only use a leaking water fill when you go on vacation. You won't know if it will work, especially if it is only used on vacation. You can always have a cup of coffee with your boiler and see that it is running properly. Not making SURE to yourself that the system is fail safe for you to not be able to attend to it is a certain path to disaster. Other things can happen to you that will take you away from tending to the boiler. Every boiler failure I have seen could have been avoided with proper testing of all boiler controls. It is in the instructions for the controls. Weekly blow offs of Mc D low water fill controls is a must. Changing electronic probes is a must (read instructions) . Testing pressuretrols and cleaning or replacing pig tails is necessary. For a home application a vapor-stat, would be more efficient than a pressuretrol. If the last radiator is warm with 1 OZ of pressure, why give it 2 lbs.

John Cockerill

BobC · March 2020

If you think that feeder is leaking by there is an easy test. Feel the pipe a foot away from that feeder. If both sides are cold there i probably water flowing. If both sides are room temperature there is no flow through that pipe.

If it's leaking by sporadically all bets are off.

Bob

acab1975 · March 2020

> @exqheat said:
> Your attitude is penny wise and a pound foolish.

it was only a thought.

Fred · March 2020

acab1975 said:
Maybe the thing to do is keep a functioning auto-feeder, but only turn the water on to it when going on vacation, and leaving it shut off otherwise.

I read his comment to say that he would keep a functioning water feeder and only turning it on when he is on vacation. I assume that means replacing the one he has with a new one and only using it when he is away for an extended period of time. That makes perfect sense.

ethicalpaul · March 2020

I'm not sure it's perfect. I wouldn't want to enable it only when going away. That would seem to increase the chances of coming home to a flooded house.

Fred · March 2020

ethicalpaul said:
I'm not sure it's perfect. I wouldn't want to enable it only when going away. That would seem to increase the chances of coming home to a flooded house.

I said "perfect " sense, not the perfect solution because there isn't one. The risk is always there that a pipe could break or a boiler failure could happen and things freeze up or a wiring short happens and burns the house down. The goal is to minimize the risk and leaving the auto feeder off as mush as possible is a smart move. Turning it on when gone for a week or two, minimizes the risk. I mean there are thousands of those units out there. They are relatively reliable.

Auto Water Feeder won't turn off

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