Low water cut off

General

We have a one pipe slant fin steam boiler with a McDonnell low water cut off. The top of the low water cut off has a red and green light (green light on all the time). Yesterday the red light came on but the auto feed did not add water so the boiler shut off. I manually added a little water and the boiler kicked on. The problem is that according to the sight glass the boiler is not low on water. There is what appears to be about 2 inches of oil on top of the water in the sight glass. Could this be the problem? We had our service guy come out yesterday and he said the low water cut off was not sending a signal to the feeder (no kidding) and he thinks the low water cut off needs to be replaced. Another problem is the lack of "dead men" in this area.... Any suggestions on what could be the problem?

KC_Jones

It could need replaced. Did you have a service done to the boiler this year? One yearly maintenance item for probe LWCO is to pull it out and clean and reinstall then test. Sometimes if they are installed with teflon tape they don't make a good ground to the block and won't work correctly. It is generally recommended to install them with pipe dope only. If it is going off on low water and it truly isn't low that could be the problem. It could also be bad as your tech suggested. I am unsure if there is a bench test that can be performed on these to verify function? Perhaps a pro could comment on that. As far as the oils, you could post a picture for us to see what you have and you will get better responses. How old is the boiler? Is it running quietly? How often does it need water? It shouldn't use much water at all over the course of the heating season. Is your tech sure it isn't a problem with the auto feeder? Honestly the water feeder not kicking on would be the least of my worries making sure the LWCO is working properly should be the primary concern.

General

Yearly maintenance was done about 2 weeks ago. That was when our tech commented that the probe looked like it would not last too much longer. He does clean the probe yearly. The boiler is only 7 years old, runs quietly, radiators are quiet. It is hard to say how much water it needs because it has an auto water feed. I have not heard it feed water this season yet but I am also at work all day. Maybe a safe bet would be to have it replaced for safety sake. I will also ask the tech about (what appears to be oil) the site glass. Thanks for the info.

KC_Jones

Does your water feeder have a meter on it to show how much water it is adding? If not I would suggest one of 2 things either get one with a meter or stop using the auto feeder. It is critical to monitor how much water the boiler uses. They should use a tiny amount of water throughout the season. Excessive water usage is what kills a boiler. All the fresh water brings in oxygen which rots them from the inside out. Just something you may want to think about.

General

Great point! I will definitely talk to the tech about it.
Thanks!

Fred

Do post a picture of the sight glass. That much oil on top of the water is unusual. Is there a lot of bounce in the water in the sight glass when the boiler is running? Have you had any piping work done on the system since it was last skimmed?

General

The tech got back with me this afternoon. He recommends to replace both the LWCO and the water feed as they work in conjuntion with each other. At the very least the LWCO if we opt for only one. The new feed will monitor the amount of water added to the boiler. The ones we have now were put on our old boiler in 1999. He said that when he let some water out of the boiler, the feed just started buzzing but would not let in water. He tried it again and it worked. As far as the LWCO, he expected it would need to be replaced because it is so gunked up every year when he cleans the boiler. Can the feed just be cleaned? He did say that what appears to be oil in the sight glass is the chemical added to the system when he cleaned it. No piping work has been done.

BobC

It's very important the low water cut off works for the health of the boiler and your safety.

The automatic water feeder is another matter. Unless you are frequently away from the house for periods of time your better off without one. They promote people to ignore the condition of the boiler until something goes wrong. I've lived with steam for over 60 years and never had one, never had a problem because it wasn't there and never had to pay hundreds to get one replaced.

Bob

Fred

If it were me, I'd go ahead and replace both. The new one will let you see how much water you are using and the new LWCO is just added security that it is way more likely to protet your boiler and your home than one that is 15 years old and questionable. Besides that, they can be moved to a new boiler if you need one in the next few years. Of course, you could clean things up and see what happens but peace of mind is worth something.

General

Both comments have valid points which I appreciate and you are absolutely right about the peace of mind Fred.

Jamie Hall

Automatic water feeders seem to generate a fair amount of difference of opinion, and I can certainly see both sides. In my view, however, there is nothing wrong with an automatic water feeder -- provided that it has a means to record the amount of water fed. Without that, it is very difficult -- indeed, nearly impossible -- to determine that you have a leak until it becomes moderately spectacular.

Without an automatic water feeder, I would not feel comfortable without two low water cutouts, the lower one manual reset, on the boiler. And as has been noted, unless you are present, a low water condition will leave the building cold. This may or may not be a problem.

General

We have decided to replace both the LWCO and the feed. They are both 15 years old and our systems seems to generate more crud than normal. I will hopefully save $$ and grief this way rather than one at a time. Do most people replace black pipe to the boiler if the gunk you are getting is extreme or just wait for when and if something starts leaking? Since all this pipe has been in this house since 1929 it would seem to me that this would be a proactive move or are you just creating more issues and spending more $$$ than necessary?

KC_Jones

Every house is going to be different, but personally I wouldn't replace pipe unless there is a problem. My house is older than yours and most of the pipe is original. There has only been work on the return piping side (small pipes) because they see all the condensate. If you have a lot of "crud" you may be getting a lot of wet steam or you may just have a lot of muck in the wet return piping. It's hard to say as again, every house is a bit different. I know the return piping that was on my old boiler was mucked up terrible some pipes blocked as much as 50%. This was mainly due to bad maintenance by the previous owner. There is only so much that can be done when you inherit one of these systems. I flushed all my returns when I put the new boiler in which you could think about doing, but honestly I wouldn't unless it is a new install. Without some valving and the ability to open up some piping it's a tough task at best and can be very messy! Just my opinion. Here is a link to what the pros say about flushing the muck out of returns.
https://heatinghelp.com/systems-help-center/how-to-flush-the-return-lines-on-an-old-steam-system/
As Dan would say it pays to wander off the wall.

General

So the cleaning should have been done when the system was installed in 07 if it was done at all. Doesn't look like a DIY project. I will quiz the tech though when he gets here. The article was very interesting and informative. Thanks!

KC_Jones

I wouldn't exactly say "should have been done" it's more like if it needs it. Mine did so I flushed them out and I won't lie it wasn't fun at all. Luckily for me the worst was in the piping I was replacing anyway so wasn't as bad as it could have been. Is your boiler set up to do a "blow down"? That helps get accumulated muck out of the bottom when it gets a bit crudy. Here is a video about near boiler piping that also mentions blow down if I remember correctly. If you can't do a blown down you can usually flush some of the muck out the bottom through the mud leg.
https://heatinghelp.com/systems-help-center/near-boiler-piping-video/

Jamie Hall

As a sort of sweeping generality, steam mains, runouts, and dry returns probably will never rust out or wear out, at least if they are pitched properly (!). Water never sits in them. Leave them be.

Wet returns, on the other hand... they may need flushing out from time to time; depending on how they are piped this may be easy or pretty close to impossible. Also, they can and sometimes do rust out, often with pinhole leaks (sometimes with many pinhole leaks -- ask me how I know!) and need to be replaced.

KC_Jones

Sorry I should have qualified wet returns. Jamie you aren't the only one that experienced leaking wet return!

General

A lot of great information and a page of questions for the tech on Monday!

KC_Jones

If your tech isn't good with steam don't be surprised if you get some blank stares.

General

In which case....I will be looking for a new tech.

General

The LWCO and feed have been installed. I have ordered and read "We have steam heat". I set the radiators to slope properly, reset the LWCO to the proper setting and I am now looking for a new service tech. If anyone can suggest someone in the Fenton, MI area I would appreciate it.