Low Water Cut Off

Ed Stuckey

The backup LWCO is at top of the bottom gage glass nut and the primary is several inches abobe to bottom nut. The fitings for the sight tube and the primary LWCO were installed at the time of manufacturing, so it is the right location.
The diameter of the equalizer pipe is 2".
The company who did the job is very reputable and have been doing steam systems for decades. They have installed many backup LWCO in residential homes successfully. This is first time they have seen this condition.
I'm a novice when it comes to steam, if the equalizer was not piped correctly would this cause the problem?
I will post another picture showing the equalizer piping.

Ed Stuckey

Low Water Cut Off

I have a one pipe steam heat system. I had an old boiler from 1925 replaced with a new Burnham IN7 steam boiler installed by a reputable company. They installed 2 low water cut off units, probe type and a UnI Match Universal Waterfeeder. The unit is under warranty so the problem I am about to describe is for my information, they still have to fix it.
The second low water cut off that they installed was for safety, it monitors the wet return, I believe. In the book We Got Steam Heat by Dan Holohan, he recommends 2 low water cut offs.
Here is the problem. After the furnace has been running for about 10 minutes, the the light on the 2nd low water cut off comes on and the burner shuts off. After the 60 second delay, the furnace burner comes on again. The burner fires for about 3 minutes and then the light on the 2nd low water cut off come on and the burner shuts down. The cycle keeps repeating until the thermostat setting upstairs is reach and the furnace shuts off. The water level in the sight tube is fine. The furnace was thoroughly flushed at installation.
The company thought the 2nd low water cut off had a short in the probe and replaced the entire unit. We thought we had the problem solved because it seemed to work. However, later on I tested the system and the problem came back. I will call the company tomorrow to report the problem.
I'm asking the question for my own knowledge, the company has to fix the problem.
I would appreciate any insight to this problem.
Thank you,
Ed Stuckey

Bill Nye_2

Ed

What is the brand name of the LWCO's? Some of the electronic ones had a thing called "Cycle guard" It will shut the burner down, on purpose, every so many minutes or so. Could this be your problem?

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Ed Stuckey

Bill,
The LWCO's are McDonnell & Miller Series PS-802 for Steam Boilers.
The LWCO that is connected into the boiler by the sight tube works fine. It is the 2nd LWCO that they installed by the hartford loop that is cycling. I hope this makes sense.
Ed

Bill Nye_2

A picture

A picture would be worth a million words here, but... near the Hartford loop?? Above the Hartford loop tee ? Below the tee? between the elbow and the tee? The picture in my minds eye says it may not be an ideal location for a probe LWCO or any LWCO for that matter. I could be way wrong but it wouldn't be the first time for that.

Could you describe where in relation to everything else the problematic control is located?

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Ed Stuckey

Picture of LWCO

Bill,
I have attached a jpeg picture of the LWCO.
Thanks you for your help in this matter.
Ed

Ed Stuckey

Picture of LWCO

Bill,
I have attached a jpeg picture of the LWCO.
Thanks you for your help in this matter.
Ed

thfurnitureguy_4

Nice cold water feeding into a hot boiler with little room to buffer????

Ed Stuckey

LWCO

I did some further testing. Here is the sequence.
Turn themostat up to turn on furnace. This is a cold start.
Furnace runs from 8-10 minutes. The red light on the 2nd LWCO, the one in the picture, comes on, the burner shuts off. There is a time delay in the LWCO, about 60 seconds. After that the red light flash for 10 seconds and the burner comes on.
The burner runs for 2 minutes and then the red light comes back on the LWCO. Wait for it to cycle and burner comes back on.
I watched this cycle for 3 more times and what is interesting is that after the initial burn it repeated the shut down every 2 minutes, almost to the second.
The water level was at its correct height in the sight tube and the primary LWCO, it is not in the picture, did not shut off.

Ed Stuckey

LWCO

The technician from the company who installed the boiler came to the house today.
He is not quite sure how to solve the problem. One thing he came up with is that pressure in the equalizer pipe, that comes of the header, is pushing water off the probe in the LWCO, which cut off continuity and shuts down the burner.
Normally, once the LWCO shuts off the burner, it takes about one minute for it to cycle and allow the burner to come on. He tried an experiment and allowed the burner to continue to fire to build more steam for a longer period of time. He then switched off the LWCO and timed how long it would take for the unit to cycle and turn the burner back on. This time it took 6 minutes instead of the usual 1 minute.
Question, is the hartford loop designed incorrectly to allow this condition?
Does anyone have any other suggestions?
The tech said he would get back to me in a couple of a days to see if he can come up with a solution.
My final options would be to have the secondary LWCO removed, since code say you have to only have one LWCO.
PS. He checked all the electical connection for polarity and proper grounding, this checked OK.

[Deleted User]

Relocate the

LWCO. Can't see if the equalizer is piped correctly. Even if it is, there is a lot of action in that pipe. Doesn't take much to uncover the probe.

Looks like that LWCO is several inches below the minimum water level label on the boiler. Most manufacturers want the backup LWCO @ the top of the bottom gage glass nut. The primary should be several inches above the bottom nut. Take a look at the instruction manual.

JohnNY

How many bushings?

What is the pipe size of the equalizer? You need to zoom out and post a better picture.


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mark smith

hire a company that knows steam ............

Ed Stuckey

Pictures of piping

I have attached some pictures of the piping.