No water visible in sight glass during operation

307TurboFire

I have a recently -installed boiler with a curious problem: Within a minute or so of the boiler turning on, whatever water is visible in the sight glass drops an inch or so, pauses at that level for about ten seconds, and then completely disappears from view.

In other words, there is no water visible in the sight glass within a minute or so of the boiler turning on.

This is the case regardless of whether the water level in the chest is at maximum or near cut-off level. In other words, this issue is independent of the actual water level in the boiler.

When the boiler turns off, within a few seconds the water level rapidly climbs back up to where one would expect it to be at the end of a run. From there, all of the remaining inch or two water that one would expect to be up in the radiators is back within 10 minutes, and we are back up to the beginning level in the sight glass.

The boiler heats the house fine and otherwise operates about as one would expect, apart from some minor short-cycling at the end of a run when ambient is below 30F, which may be due to lack of an anticipator setting on the thermostat, or perhaps we need some more venting.

The boiler mfr and installer are both very reputable. I am not going to use their names here.

I have reviewed the near-boiler piping based on my own amateur knowledge, and I have also compared and contrasted it with the mfr's installation specs. I have also reviewed it with another amateur who has over 60 years of experience as a user/operator of household steam heat, and he has also compared to mfr's installation specs. We don't see any obvious problem with the piping.

It seems like there is some kind of funky localized pressure issue inside the boiler that forces all of the water out of the sight glass without causing any other obvious problems.

How serious is this? Will it impact longevity of the boiler?

ChrisJ

If a boiler is firing and there's no water in the gauge glass, it needs to be shut down. PERIOD.

The first thing I'd look at is the low water cut off.
The second thing I'd look at is dirty water.

KC_Jones

Was the boiler skimmed after installation?

What you described is typical surging from oils being inside the boiler. If the boiler was not skimmed it needs to be skimmed which should solve the problem. Sometimes skimming needs to be done more than once depending on how much piping was changed when the boiler was installed.

That said, if you are so inclined, post some pictures of the install and we can review the piping just in case there is some subtlety that could be amplifying the problem.

307TurboFire

It's been skimmed at least twice so far. There was an interlude that involved a different operating condition with a lot of wild surging up and down before the most recent skim. The water was made more basic, which dampened the surging, but a bit later it reverted back to this operating condition where the water is completely disappearing during operation.

We do still smell some of the start-up odor, but this boiler has been operating for close to a year now.

My first reaction was oh my, shut the boiler off. The low water cut-off is functioning and has been tested. The low water cut-off seems to function completely independently of what is visible (or not visible) in the sight glass.

ChrisJ

307TurboFire said:

It's been skimmed at least twice so far. There was an interlude that involved a different operating condition with a lot of wild surging up and down before the most recent skim. The water was made more basic, which dampened the surging, but a bit later it reverted back to this operating condition where the water is completely disappearing during operation.

We do still smell some of the start-up odor, but this boiler has been operating for close to a year now.

My first reaction was oh my, shut the boiler off. The low water cut-off is functioning and has been tested. The low water cut-off seems to function completely independently of what is visible (or not visible) in the sight glass.

Probe type LWCO?

Without being there, going by your description I'm guessing the water is dirty, causing foaming which is tricking the LWCO.

We need some pictures ASAP and personally, I'd shut it down and get it straightened out.

nicholas bonham-carter

I had just that condition, and it can stress the boiler sections, leading to early failure.
Look for any horizontal section of pipe in the return, whose height is slightly above the boiler water level, when measured from the floor.
Such a pipe can “hide” a lot of water as the pressure causes the height of water in the return to rise 1.75 inches for every ounce of pressure.
Weil McClain do show an alternative boiler piping with a horizontal reservoir.—NBC

Jamie Hall

Plain and simple: do NOT run the boiler unless water is visible in the sight glass. I am, frankly, horrified that you have let it go this long.

The low water cutoff should shut the boiler off before the water disappears. If it doesn't, it is suspect -- and not doing what it is supposed to do (there is a reason I like float type LWCOs as one of the two LWCOs on any boiler). Again, a reason to shut off the boiler and keep it off until the problem is found and fixed.

The timing you mention indicates that the water level is dropping pretty much as soon as the boiler starts producing steam. Is there a Hartford Loop? Is it properly connected to the equalizer?

As @nicholas bonham-carter said, operating under that condition can stress the boiler sections -- or their connections -- leading to early boiler failure. Perhaps a little more seriously, if for some reason cold water were introduced into the boiler with the water level low like that, you might get lucky and only have an immediately cracked section. You might not get so lucky, and have a total failure quite abruptly.

EBEBRATT-Ed

@307TurboFire

If you can't see water in the gauge glass the boiler is not safe to operate. Period. That is what the gauge glass is for...so you can visually see the boiler water level is in a safe condition.

Chances are the piping is wrong or the boiler still needs to be skimmed properly.

I would immediately check the low water cutoff to make sure it shuts the burner down on a low water condition. It may not be wired correctly

Fred

It needs a good skim. It may have been skimmed twice already but what you describe is exactly what happens when there is oil in the water. How was it skimmed? Draining the boiler is not a skim an, if it takes a half dozen skims to clean it up, then it takes a half dozen skims. Skims are very very slow and from a tapping above the normal water line.

ethicalpaul

The low water cutoff should shut the boiler off before the water disappears. If it doesn't, it is suspect -- and not doing what it is supposed to do (there is a reason I like float type LWCOs as one of the two LWCOs on any boiler). Again, a reason to shut off the boiler and keep it off until the problem is found and fixed.

This is where the Cyclegard is actually pretty good. I know that my probe really doesn't shut off my boiler if the water level drops during firing. Only after boiling stops does it raise the alarm. The boiling keeps it wet enough even with a significantly low water line.

ChrisJ

A steamer firing without water showing in the gauge glass is a lot like this guy.

stevenknaub

I had the same problem you are describing. My installer omitted the equalizer pipe. Equalizer pipe connects at the end of the header then drops below the water line and back into an opening specified by the manufacturer. It equalizes pressure above and below the waterline, without it, the steam pressure drives the boiler water into the “cold” or “wet” return, and that is why the water in the sight glass is disappearing, and then returning when steam is no longer being produced

SteamingatMohawk

There is no mention of the pressure in the boiler when the situation occurs. What is it?

jhrost

Ethical Paul :

Is your boiler probe right at the point where the manufacturer says is the minimum water level, or somewhat above? My boilers probe seems to be quite a bit above where the Mfg actually has the minimum water level marked off.

I have found this to be irritating to the extent that once the boiler turns off and the roiling stops the probe may not be in contact with the water anymore. But maybe it is actually a good thing in that it gives you information well before damage is actually done - a water feeder with a 5 minute delay would work in my case.

Not to diverge too much from heating , but the warning you get in an automobile is far less forgiving. If your engine oil light comes on you have very little time to act before your engine is ruined. Theoretically someone is always looking of course. But it would be nice to have a "gauge glass" in your car that gave you the same info you get from checking with a dipstick. For that matter a heat gauge is much better that just a warning light for engine coolant temperature because it gives you time to see a trend and maybe tighten up the clamps on your hoses or something before you get a boil over condition.

But to get back to boilers the more info you get and the sooner you get it the better. Of course the boiler has these backups - low water cutoff - pressure gage - water feeder if you have one , and Hartford loop - though some of these are more useful than others. Even though it seldom comes into play the pop safety valve at least rescues you from a total catastrophe. And it isn't distracted by texting etc like a modern driver who needs to make critical assessments might be.

To make another analogy - this site is kind of like boiler drivers ed for homeowners.

ethicalpaul

Mine is a Utica PEG and they don't seem to define a "lowest permissible water line" but I can tell you the probe is about at the same level as the bottom port of the sight glass.

jhrost

Interesting. Mine is a dunkirk and the mark they have near the bottom of the sight glass with the bold letters "lowest permissible water level" is quite a bit below where the water level in the sight glass is ( at least 3 inches I would say) when the low water cutoff kicks on.

It has been that way since I made the mistake of getting it installed. The probe is housed in the same section of the boiler as the site glass, but on the opposite end of that section. It seems to correspond in height above pad to where the water level is when the lwc cutoff is activated after the thermostat shuts off the boiler. The effect is to always trigger the low water cutoff to feed after a burner cycle, with the resultant overfilling of the boiler by the time the condensate comes back. I set the maximum dwell time, but that is only 2 minutes and I think I need about 5 before enough condensate gets back.

I ended up just shutting the valve to the feeder so it goes through the motion of feeding water without actually doing so. In a way it is a robust test of whether the low water cutoff is working since it is activated multiple cycles in a day, while some people have to actually test their low water cutoff annually.

nicholas bonham-carter

Jhrost, what is your pressure, when firing?
Remember that for every ounce of pressure, the water level in the returns will rise 1.75 inches, and so with over-pressure, the boiler can be starved of water, as water fills the pipes.
That’s why we like a good low pressure gauge, marked in ounces, (0-3 psi.)—NBC

jhrost

I'm sure you are right about the low pressure gauge. I've got the pressuretrol set at the .5 cut in and 1.5 cutout as near as I can determine. The pigtail is also cleaned out. The original 15lb pressure gage seems to rise by about 8 or 9 ounces of pressure when firing , how accurate it is I don't know. It doesn't short cycle , and shuts down when the thermostat is satisfied. The boiler capacity and radiation are a reasonable match, which is one of the few right things they did in the installation.

One of these summers if I am still alive I would like to try putting in a replacement. So in the meantime I've invested in main and radiator vents , but haven't bothered to replace the water feeder or put in a low pressure gauge - the near boiler piping is a whole other story. It requires a lot of attention but I muddle along. I'm hoping that if I absorb enough from following this sight I might be up for the challenge of an installation in the future. I should probably add that to the what you procrastinate about thread.

SteamingatMohawk

After all this discussion, are you going to continue to operate the boiler with no water visible in the gage glass? I don't think I have seen where you have eliminated the problem.

dopey27177

Based on what you told us about the site glass I believe your boiler is causing a water surging condition.

The boiler needs to be cleaned chemically. Get in touch with the boiler manufacturer and ask how to clean the internals of the boiler and what chemicals they recommend.

Back in the day when I worked as a boiler installer we filled the boilers up to the top of the boiler, added the recommended chemicals through the safety valve port heated the boiler and water with the burners. Used the aquastat as the control (Made hot water with a submersed coil) to heat water to 180 degrees Ran the boiler for two hours and then drained the boiler when cooled. Set boiler up for operation, came back about a week later and repeated the action.

Came back a week later and skimmed the boiler.

This was a lot of work for a mechanic and helper.

After all was done and the boiler was operating correctly we installed Steam master tablets into the boiler. We used 1/3 the tablets recommended, this prevented foaming and turned the water slightly blue purple,

Jake

PS
do not operate the boiler till you get a stable water glass.

When you look at the gauge glass you should be able to see water being replaced at the top of the gauge glass,

ethicalpaul

jhrost said:

It has been that way since I made the mistake of getting it installed.

Well said @jhrost ! A sentiment many have felt, if not shared

ChrisJ

dopey27177 said:

Based on what you told us about the site glass I believe your boiler is causing a water surging condition.

The boiler needs to be cleaned chemically. Get in touch with the boiler manufacturer and ask how to clean the internals of the boiler and what chemicals they recommend.

Back in the day when I worked as a boiler installer we filled the boilers up to the top of the boiler, added the recommended chemicals through the safety valve port heated the boiler and water with the burners. Used the aquastat as the control (Made hot water with a submersed coil) to heat water to 180 degrees Ran the boiler for two hours and then drained the boiler when cooled. Set boiler up for operation, came back about a week later and repeated the action.

Came back a week later and skimmed the boiler.

This was a lot of work for a mechanic and helper.

After all was done and the boiler was operating correctly we installed Steam master tablets into the boiler. We used 1/3 the tablets recommended, this prevented foaming and turned the water slightly blue purple,

Jake

PS
do not operate the boiler till you get a stable water glass.

When you look at the gauge glass you should be able to see water being replaced at the top of the gauge glass,

Jake,
What does this mean?

SteamingatMohawk

@dopey27177 Can I assume you are using the term site (actually sight glass), gauge glass and water glass interchangeably?

Precaud

dopey27177 said:

When you look at the gauge glass you should be able to see water being replaced at the top of the gauge glass,

Really? I've never seen that on mine. The level just creeps up, I assumed from the bottom. Perhaps I haven't watched close enuf.

ChrisJ

> @Precaud said:
> (Quote)
> Really? I've never seen that on mine. The level just creeps up, I assumed from the bottom. Perhaps I haven't watched close enuf.

The top is a vent. You should never see water coming from the top, it means your water line is incredibly unstable.

Precaud

ChrisJ said:

The top is a vent. You should never see water coming from the top, it means your water line is incredibly unstable.

That makes sense.

Fred

Wow, the top of the glass should be bone dry. If there is water or condensation there, it's time for a good skim!

Hap_Hazzard

Precaud said:

dopey27177 said:

When you look at the gauge glass you should be able to see water being replaced at the top of the gauge glass,

Really? I've never seen that on mine. The level just creeps up, I assumed from the bottom. Perhaps I haven't watched close enuf.

I see it all the time.

Hap_Hazzard

ChrisJ said:

> @Precaud said:

> (Quote)

> Really? I've never seen that on mine. The level just creeps up, I assumed from the bottom. Perhaps I haven't watched close enuf.



The top is a vent. You should never see water coming from the top, it means your water line is incredibly unstable.

Well, it is boiling.

ChrisJ

> @Hap_Hazzard said:
> (Quote)
> I see it all the time.

Can you share a video of this on YouTube or equivalent?

Water spilling over the top of a gauge glass is typically considered very bad.

Hap_Hazzard

Fred said:

Wow, the top of the glass should be bone dry. If there is water or condensation there, it's time for a good skim!

Seriously? Would it surprise you to know that water goes all the way up into my header when the boiler is making steam? I even have an equalizer to return the water to the boiler. My point is: water gets everywhere.

New England SteamWorks

Assuming a moron did not pipe it, sounds like it just needs skimming. Lots of oil can easily cause the gauge glass to empty while there is still water in the boiler. No water should drip from the top of the gauge glass. If it does, confirmation of the need for skimming. Share pic of install.

Hap_Hazzard

It doesn't drip. It runs down the inside of the glass. If you've never noticed this you're probably not looking very closely, or the upper glasscock is closed.

I recently skimmed my boiler, and I piped it. If you want to call me a moron, I think that's a reflection on you.

ChrisJ

Hap_Hazzard said:

It doesn't drip. It runs down the inside of the glass. If you've never noticed this you're probably not looking very closely, or the upper glasscock is closed.

I recently skimmed my boiler, and I piped it. If you want to call me a moron, I think that's a reflection on you.

I've stared at mine for hours, water doesn't run down. Steam cannot get into it and if the top was shut the water wouldn't move (no vent).

@KC_Jones Does water run down the top of your gauge glass? I'm sure you noticed while polishing copper for hours...

Hap_Hazzard

Okay @ChrisJ.

Fred

Hap_Hazzard said:

Fred said:

Wow, the top of the glass should be bone dry. If there is water or condensation there, it's time for a good skim!

Seriously? Would it surprise you to know that water goes all the way up into my header when the boiler is making steam? I even have an equalizer to return the water to the boiler. My point is: water gets everywhere.

I'd have to say "yes" I'm surprised. That's not normal, @Hap_Hazzard

Fred

@ChrisJ , doesn't run down my gauge glass either and trust me, I've watched it very closely. I also have to say water doesn't go all the way up to my header either, like it does for @Hap_Hazzard

STEAM DOCTOR

Water should never run down the glass. Top of glass should be clean and dry as a bone.

SteamingatMohawk

For those not aware, here is a quick lesson on gauge glasses. Refer to the views in the attached cut from a typical manual (HB Smith GB200 series boiler, which I have). In the sketch the gauge glass is referred to as a water level indicator. Don't let it confuse you.

In the sketch, the water line for this boiler is 23-1/4" above the floor the boiler stands on. The gauge glass connects to the water/steam side (not the flame/heat side) of the boiler at two locations. The lower connection of the gauge glass is below the water line and the upper connection is above the water line.

For the gauge glass to be accurate, the top connection needs to be open/unclogged. Otherwise, changes in water level are impeded because of the trapped air/steam at the top of the gauge glass.

When the boiler is running the space fills with steam, when the boiler cools down air enters the boiler.

If the lower valve is shut or the bottom connection is clogged, the water level in the gauge glass can't go up or down.

I hope this helps.

Hap_Hazzard

Fred said:

Hap_Hazzard said:

Fred said:

Wow, the top of the glass should be bone dry. If there is water or condensation there, it's time for a good skim!

Seriously? Would it surprise you to know that water goes all the way up into my header when the boiler is making steam? I even have an equalizer to return the water to the boiler. My point is: water gets everywhere.

I'd have to say "yes" I'm surprised. That's not normal, @Hap_Hazzard

Not normal for carryover to reach the header and return via the equalizer?

Hap_Hazzard

SteamingatMohawk said:

For those not aware, here is a quick lesson on gauge glasses. Refer to the views in the attached cut from a typical manual (HB Smith GB200 series boiler, which I have). In the sketch the gauge glass is referred to as a water level indicator. Don't let it confuse you.

In the sketch, the water line for this boiler is 23-1/4" above the floor the boiler stands on. The gauge glass connects to the water/steam side (not the flame/heat side) of the boiler at two locations. The lower connection of the gauge glass is below the water line and the upper connection is above the water line.

For the gauge glass to be accurate, the top connection needs to be open/unclogged. Otherwise, changes in water level are impeded because of the trapped air/steam at the top of the gauge glass.

When the boiler is running the space fills with steam, when the boiler cools down air enters the boiler.

If the lower valve is shut or the bottom connection is clogged, the water level in the gauge glass can't go up or down.

I hope this helps.

Right. And, since the top of the gauge glass is only about three to four inches above the water line, it doesn't take an unusual amount of surging to cause some water to enter it and run down into the glass.