Auto Feed Running when boiler is filled

JH3550

A few weeks ago when I was flushing water out of the low water cut off, my auto feed kicked on and wouldn’t turn off. I finally had to shut the water off to the auto feed because I was afraid it was going to flood the boiler. I remembered reading something about lightly tapping the water cut off with a hammer so I very lightly tapped a couple of times and then the auto feed shut off. Since then, this happens every time I blow down the boiler, including the very light hammer tap. This has not happened in past heating seasons.

Do I need to do anything about this? What do folks recommend?

One pipe steam. House built in 1924. We’ve lived here two years. Boiler is about 20 years old. Not sure of the age of the auto feed or low water cut off.

Thanks!

Jamie Hall

Theoretically the autofeeder can be taken apart and the little solenoid valve which is sticking on you repaired. Theoretically. In practice it's usually easier to simply replace it — nice new VXT complete with useful delays and volume controls and a flow meter…

EBEBRATT-Ed

Probably not the auto feeder if you tapped the low water cutoff. The low water cutoff needs to be taken apart and cleaned. The low water cutoff turns the water feeder on and off and the float is probably sticking. If you don't have it cleaned it could fail to shut the burner down in a low water condition ……and you do not want that.

You should have the LWCO serviced. In the meantime, keep water in the boiler by feeding it manually if you have a bypass piped around the water feeder. Can't tell by the pictures.

Keep your eye on the water level until you get it looked at.

The VTX feeders are better than the McDonnell Miller as @Jamie Hall mentioned.

delcrossv

Those MM LWCOs should be stripped down annually.

Probably a bad switch, but those are sold with the float, so $$$.

JH3550

Thanks! I was thinking it might be the float in the LWCO sticking. Is cleaning that something a plumber might do or do I have to get a steam person? So far I haven’t found a steam person working near me for smaller jobs like this. (Central Westchester County, NY)

Jamie Hall

Maybe I'm confused. In the first post, you mentioned that you tapped the water feed and it shut off. I'm sorry, but I took you literally. If you meant you tapped the float chamber or switch — the MM67 — and it shut off, then you have a sticking float or bad switch. The switch assembly is not that hard to replace (make sure you note what is connected to what, though!). The float is a little more difficult, but also quite doable.

First thing to do, though, is to blow the assembly down — hard — several times and check the switch operation. It may just be gunked up.

JH3550

I tapped the LWCO, not the auto feed assembly

Sounds like it’s the float getting stuck in gunk. Ill try blowing it down hard as suggested and if that doesn’t work, try to get someone in who can clean it.

EBEBRATT-Ed

@JH3550 You could PM @Mad Dog_2 or @JohnNY if they can't do it they may know someone that will. You could clean it up yourself if your handy, but it is kind of a dirty thankless job.

@delcrossv you can buy a #2 switch for a 67 without the float.

Steamhead

@JH3550 et al, if that boiler can be fitted with a probe-type low-water cutoff, that's the way to keep this from happening again. Take a pic from the front of the boiler so we can see what's there.

JH3550

@Steamhead

Pic from the front

EBEBRATT-Ed

Probably the lower tapping on the 67 could be used for an electronic. May or may not be 3/4" may need a 1/2" probe

ethicalpaul

Unrelated, but consider turning down your pressuretrol to the bottom of its range:

JH3550

@ethicalpaul I previously turned it all the way down and the boiler wouldn’t come on when the thermostat called for heat. I’ve got the cut in as close to .5 as I could.

ethicalpaul

OK that's good. Those controls are abysmal so we all have to do the best we can with them!

JH3550

My plumber came over today. He said it would be easier to just replace the float type LWCO rather than switching to an electric probe style. But he said he can do either. From what I’ve read on this site I was leaning towards switching to the probe.

What are peoples’ thoughts on just replacing what I have or switching to the probe?

Thank you!

Jamie Hall

They both work. They both need maintenance. I like the float type, as it's simple and easily repaired — and very easy to routinely check (the "test" button on the probes checks the circuitry — but not the actual function of the probe) when you blow the float chamber down… but that's me.

ethicalpaul

They both do need maintenance…one needs weekly maintenance, and one needs annual maintenance, if that. One has moving parts exposed to boiler gunk, and one doesn't.