Water level mysteries

danmayer175 · January 24

I can't come up with any explanation for what I see my water level doing. In a cold state I have the water at 1/2 of the glass. Bear in mind, this puts the water about 3 inches above the manufacturer's normal water line - because the installers elevated the LWCO and gauge. And 3 inches closer to my already too close header - I now have only about 10 inches from center of glass to bottom of header. So it seems likely that a good bit of water is being thrown into the header and maybe finding its way out of the boiler. And that would probably explain why the water drops so much on every firing - it bobs around 1/10 of the glass most times, very close to the cast line of the LWCO. Which would explain why the LWCO calls for water all the time (the feeder is shut off but still reporting how much water it 'thinks' it's delivering).

Eventually all that water comes back. After a cool down, and without any feed, I end up right where I started - glass half full. OK that makes sense - there is too much water leaving the boiler and taking its time getting back. It's not ideal, but it does heat the house, and I don't have water hammer problems (unless the system gets flooded by the feeder).

But on some cycles there's a completely different result that I can't make sense of:

Shortly after firing ends, the water level (which was bobbing around 1/10 of the glass) begins to rise - not steadily but in gulps sort of - way above where it started. After a minute it's over the top of the glass. After things cool down a bit I feel around for heat from the water line and it seems to be about 2" below the top of the jacket - which I think means the sections are full.

When the next cycle starts up, all that extra water disappears quickly. Within 1 minute the water level is back at 1/2 glass, and then as steam develops it drops down to its normal firing level.

The only explanation I could come up with is a constriction in the wet return. I think there's actually a surplus of water in the system. But it's reading 1/2 glass because a bunch is stuck in the wet return. And then at some point it builds up enough condensate to push through and refill the boiler?

EBEBRATT-Ed · January 24

Sounds like that could be the problem.

But you may have other issues. Post some pictures of the boiler and the piping around it. Has the boiler ever been skimmed.

danmayer175 · January 25

I've lived here 10 years and never had it skimmed.

Here are the near-boiler sins I've uncovered to date.

And here's that reducer tee 8 ft down the main. I suspect condensate from this runout collects behind this reducer. It's a tiny pond, but if the top of the ramp created by the reducer is a hair higher than the inlet from the riser, then the condensate from that runout drains back down the riser.

If both those runouts are returning via the riser, there's about 140 sq ft. EDR worth of condensate that never gets to the wet return. Maybe that's a clue?

EBEBRATT-Ed · January 25

yeah the piping is not great. header too low, they should have brought both supply mains down to the boiler header and dripped the counterflow one and yes the reducer tee is not great

The Hartford loop should be 3-4" below the normal water level so that is ok.

109A_5 · January 25

Personally, if it was my system, after the heating season I would correct the LWCO / sight glass height issue. It seems like it is baiting you to run the water level too high, aiding in causing strange issues. In the mean time, what happens if you run it just above the level the LWCO would keep it at (if it has an auto feeder) or just above that (no nuisance burner shut downs), but not the 3.25 inches above maybe only 1 to 1.5 inches above ?

If you get ambitious the other near boiler piping issues could be corrected too. However if the water level is run a bit lower some of the other odd issues may go away or be reduced.

danmayer175 · January 25

@109A_5

"run it just above the level the LWCO would keep it at (if it has an auto feeder) or just above that (no nuisance burner shut downs), but not the 3.25 inches above maybe only 1 to 1.5 inches above ?"

Do you mean cold fill to that level? I haven't tried that. There seems to be a level where it likes to boil, regardless of where I fill it to cold. About 1" above the manufacturer's NWL. Maybe that's where it gets just far enough from the header to stop throwing water? I always fill above that and watch it boil down, but maybe if I start there it will lose less water? It's just so close to the LWCO cast line that the slighest bob or surge signals a call for water.

109A_5 · January 25

With most correctly installed boilers there is a wide water level range, a 'Sweet Zone' (as I call it) that provides normal trouble free operation, a usable water level range. Since your near boiler piping is incorrect this may be causing you the issues you are having. To make it even more troublesome the installer raised the M&M 67 LWCO and the sight glass. So with a normal correct installation you probably could run the water level anywhere from where the LWCO shuts the burner down (no auto water feeder) up to about 3/4 of the sight glass with no problems.

Since your LWCO and the sight glass has been raised up 3.25 inches (maybe close to half the sight glass range) you can't use the lower portion of the normal usable range since the LWCO will shut the burner off. Also you may not be able to go as high as a normal 3/4 of the sight glass since the near boiler piping is incorrect causing other issues. So the normal Sweet Zone of 1/3 to 2/3 (in a normally positioned LWCO and sight glass) on your system may be compressed into a much smaller range (if it even exists at all) that you will have to find and it may need a lot more attention to keep it in that range. Come Spring I would normalize the M&M 67 LWCO and the sight glass per the manufactures instructions (no 3.25 inch offset).

As an example; If the M&M 67 LWCO also controls a water feeder the burner should never shut off due to low water. The switch in the M&M 67 LWCO usually has a dead band where it calls for water first. If the call for water is not satisfied and the water drops just a bit more then the burner will be turned off.

danmayer175 · January 25

@109A_5

That all sounds right. There's only about an inch between bottom (cutout) and the top (the height where water is so close to the header that it just won't stay in the boiler when it's firing).

I was thinking of replacing the CG450 first (I have both a float and probe LWCO). And re-wiring so I could see how it runs at spec level before redoing the MM67 piping. I'm still worried that correcting the level will create a problem at the Hartford loop. The close nipple is 2" underwater now, but after correction it will be half-wet, half-dry.

109A_5 · January 25

From your past pictures, I can't tell (maybe I missed a picture), if the probe for the CG450 is lower than the minimum water level line cast into the M&M 67 housing. Maybe just use the CG450 as the LWCO if it functions correctly. However in doing so you may not see any water in the sight glass when the water gets low, which is not good.

Look into a Gifford loop, Gifford claimed it was better than a Hartford loop which was a minimum to satisfy the Hartford insurance company back in the day before electric LWCOs existed.

One reference;

https://www.semanticscholar.org/paper/An-improvement-to-the-Hartford-Loop-Gifford-Flothow/4a456470e37383fd6d4ad2f79d62e60c6be052d6

danmayer175 · February 2

Found another clue to the mystery. The CG450 LWCO is disabled. At some point it was re-wired to work as nothing more than a junction box for the MM67.

So I think the original install had just the CycleGuard. But there must have been problems. And the fix was to abandon the CycleGuard and add an MM67. But there were still problems, so they raised the waterline.

109A_5 · February 2

It think the CG450 may have been a later addition or a redundant LWCO. The M&M 67 is older technology, why would most folks add older tech ? And the sight glass is set up with the M&M 67 and not where the boiler manufacture intended. I would start my normalizing the sight glass and the M&M 67. Hopefully Mr. Gifford is correct and that won't be an issue. Maintaining the proper (manufacture intended) waterline may help with the excessively low header.

The sight glass at the higher elevation is not doing you any favors.

danmayer175 · February 2

I finally caught it in the act! The pipes were just cold enough, and the water just warm enough to get a good bead on the waterlines. Water in the boiler is 'perched' about 6 inches higher than the wet return. No pressure differential. No vacuum in the boiler. So there must be something in the wet return acting like a leaky check valve. If I let the boiler sit like that without firing for a few hours, the waterline eventually equalizes. In photo below, the yellow zip tie is the waterline in that pipe. The laser is the waterline from the wet return.

109A_5 · February 2

Interesting. Although that would not be a lot of water once the level offset bleeds back into the boiler given time. If the wet return on the boiler side of the Hartford loop is restricted and the majority of the wet return condensate actually needs to flow backwards up through the equalizer to return to the boiler that cold be an issue.

When in this state you described can you tell if the condensate level is also high at the drip end of the wet return ?

If the wet return on the boiler side is restricted it may have to come apart to clear the restriction so at that time the low header height and the other header issues could be corrected.

Water level mysteries

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