Boiler Cut Off

BAB

I have a 6" main that elbows down & into the top of the boiler with two 4" steam outlets. One of the 4" outlets is directly under the downward facing 6" 90 degree elbow.  At random times this lack of a drop head piping arrangement causes problems.  The emergency shut off is triggered because of the boiler water level bouncing up & down about 3/4" - one inch.  Most of the time the McDonnell & Miller Series 47 Low Level Feed/Cut-off will do its job.  But every now & then the boiler is shut down & my building gets cold.  I have been monitoring this problem for some time & checked out many potential problems, ... leaky steam up the stack,  Series 47 trouble shooting, etc. 



As a solution I I was going to drill & tap a 3/4" drop drain line into the 6" main 3' horizontal run just above the boiler.  The drop drain line will have a Turstall Float & Thermostatic steam trap or a Barnes & Jones 122A Steam Trap then returned to condensate.  Or I could just pipe the drain direct to the equalizer piping near the boiler.  My steam is  low pressure, usually less than 3 oz per sq inch.



The drain line should catch most of the returning condensate causing the the boiler level bouncing.  I would appreciate some critical comments.  You guys have never held back on me before so have at it.  My steam knowledge has been 60% from the books sold on this site, 40% from this chat forum and 0% from local piping/steam/distributor "experts".  

jpf321

so to be clear ...

You feel that condensate dropping directly into your boiler through a 4" riser from a 6" overhead is causing your boiler water to bounce and therefore causing your #47 to trip?



I'm suspect of the immediate presumptive jump from condensate dropping is causing #47 to shut off.



I'm not sure that a LWCO would be so sensitive to a 3/4"-1" bounce. What if you just overfill by 1/2"?



Is the #47 manual reset? Why is it that sometimes your boiler is staying off and sometimes it's not?



when was the last time you skimmed the boiler? What chemicals, if any, have you added to the boiler?



sorry more questions than answers ...

Jamie Hall

I would be very surprised...

if there was enough condensate dripping down and making all the way down the 4" riser to cause the water level bouncing.  Remember, the steam from the boiler is going up that header at a pretty lively clip.



I could well be wrong -- I have been, many times before -- but the bouncing is more likely to be more or less normal, although it is possible that a bit of skimming or blow down might improve matters a little.



And, unless your water level is kept low (what I would regard as abnormally low) in the boiler, the LWCO shouldn't trip on that much bouncing.  I like to see the water level, steaming, "bouncing" (if it does) right around the half way mark on the sight glass, or a little higher (depending on the installation).  On an 8" glass, you'd have to have a 4" bounce to trip... so I'd kind of keep an open mind as to what else might be tripping the LWCO.

BAB

Boiler cut off continued

I skim at the beginning of each heating season & then again in 2-3 weeks.  I think our last skim was a about a month ago.  We used chemicals after new boiler install over 5 years ago and once or twice thereafter.  We have not used chemicals for at least 2 years.  The boiler water level is set to ride in the middle to upper middle of the 8" sight glass.  After a long pause after then last fire up the level may rise to the 6" - 7" level.



We have five heating zones.  If the close or small zone calls for heat the boiler is on/off in 10 -20 min.  If a distant (200 feet away) or large zone calls for heat the boiler will run for 15 -30 min.  When all five zones by happenstance all call for heat at the same time it will be on for about 30 min.  All this is in real cold weather.  My time estimates are estimates.  I have never been monitored at length in detail, .... just from my general observations.  My office is in the basement 20 feet from the boiler.  I check the boiler every morning or so, ... record hour usage, cycles, & outside temperature.  I drain some water from the Series 47 at that time.  I might drain again once or twice a day.  We have very clean boiler/condensate water.  This is not from just my own observations but when the burner tech or plumber are around they tend to independently comment on the clean sight gauge.



Everything does appear to be on target & as it should be for days or weeks.  Then out of the clear blue, no drastic change in weather or me tampering or non tampering and the dreaded little red light will turn "on" at the emergency shut off box & I know the boiler is down.  I spend a lot of time watching the boiler & it's cycles, .... it will never shut off randomly in front of me.  If we have someone over for dinner, if I want to go out for the evening or want a good night's sleep ,.....that is when I get a phone call that the building is freezing & I know the boiler shut off.



When the boiler goes thru the above cycles it may or may not get close to "low" level.  With the different cycles, and the condensate pump kicking on, the boiler water level usually does not get too close to the low level, it will hover in the mid to upper mid range.   When it occasionally gets close to the low level the Series 47 adds feed water until satisfied.  If the requested water feed is not enough the Series 47 cuts off the boiler for 15 -60 seconds until enough feed water is added then the boiler turns on again.



I read two of the replies to my question & they both say the same to me, .... do not attempt your unnecessary piping scheme & examine the shimming/clean water status.  I will investigate & let you know.  In the mean time if you have some other/additional observations, ... we appreciate the comments.     

Jamie Hall

Oh ho! The plot thickens...

There is a condensate pump on this thing?  What controls that?  Is it a true condensate pump -- activated by the level in the receiver -- or is it a boiler feed pump, activated by the boiler water level?  If I had to cope with one of those devils, I would prefer the latter hookup, with makeup water determined by the water level in the receiver.  Makeup water would go into the condensate receiver, not the boiler.



If it is the former -- for that matter, in any event -- I would be very much inclined to check the controls on that condensate pump, and if it is the former I would also be inclined to attribute my headaches to some combination of slow return  from one or more of your zones, and possibly a wonky control, and the phase of the moon...



Tell me more...

BAB

boiler cut off continued

The condensate return pump used to be a vacuum return pump setup with it's own receiving tank.  We do not use the pump or the steam system as a vacuum system anymore.  When the remote pump/tank fills up the pump turns on.  There is no pump flow surge.  The #47 is mounted direct on the boiler.  Water feed requests from the #47 send fresh water from a 1/2" copper pipe into the 2" black iron boiler condensate return/water feed line. 



Jamie, you mentioned a slow return from one of my five zones, Zone #5.  This problem zone is in excess of 200 feet from the boiler.  I used to have a **** of a time to get steam back there until I installed many, many Gorton air vent valves.  I also altered all of the drop legs directly after the thermostatic traps to bleed air.  The air used to get caught in the drop legs & not allow the radiators to pass steam.   Yes, whenever I have to send heat to that Zone #5 there will usually much low, low level action.  Your mention of slow return reminds me that we had a lot of scale/sludge in the piping near the boiler & condensate return pump (vacuum pump).  All of my condensate return piping is easily accessible so I could pull some open for inspection.   



Jamie,  Thanks for the suggestions & attention to detail.   

jpf321

not only a pump ...

but zones ... how are the zones set up/being controlled? is water being trapped in a zone(s)? are zone valves sticking closed and therefore raising pressure enough to trip manual reset pressuretrol? how do we even know this is a water level problem? how is the boiler "reset" to bring it back on line? are we sure this isn't a pressure problem?



all you need is one sticking zone valve and have that zone be the only one calling at the moment and you are in high-pressure city. if that zone is stuck and any other is calling, you would probably be OK and not trip on pressure since the steam has somewhere to go.



we need (fairly close-up) pictures of ALL boiler controls and all possible reset buttons. as well as pump controls. as well as a detailed account of what you actually do to bring the boiler back into operation.



i do not think this is a waterlevel problem. how much FRESH auto-feed water is added each day? each week?

BAB

boiler cut off

Regarding a zone Honywell/Jamesbury motorized control stuck closed, ... we did have that happen last heating season & the boiler did shut off because the pressuretrol was activated at 3 psi.  We repaired the valve & have not had another high pressure shut off since.  On the high pressure shut off the rooms or zone will be hot, over heated.  You might say why are the rooms overheated if the steam valve is stuck closed?  The answer is that the overhead & exposed steam lines get so hot that they overheat the rooms more than the shutoff radiators.  Our valves are so old that they do not close 100% anyway, ... so on high pressure  they leaked.  We no longer have a broken valve problem.  Our system is always under 0.5 psi, actually runs at about 3-4 oz per square inch, vapor pressure.



The only mechanism that turns the boiler off is the emergency low low level probe, ... a separate device from the Series #47.  I am home now so I do not have the manufactures name.  The black box has a red light on top that lets us know the boiler water level was too low thus activating the boiler cut off.  We then push the emergency level control reset button & the boiler turns on again. 

jpf321

where in...

the piping are the zone valves?

off the boiler headers? do all pipes services by the zone valves have a mechanism to get water back to the boiler? you aren't counting on a counter-current return through the header and yet shutting off a zone valve that would make that return impossible?

maybe your black probe box looks like this (MM #801)... has the probe been cleaned recently? was teflon used on the probe threads? (this is a no-no http://completewatersystems.com/wp-content/uploads/2011/05/1428.pdf Step 1.b. see warning box)

BAB

Boiler cut off

God Damn you guys are fast.  I can not type fast enough.



The 6" main header feeds the five zones.  The zones are (3) 3" and (2) 2-1/2" pipe size, or visa versa.  All have the same Honeywell/Jamesbury motorized control with one valve feeding 10 -12 radiators.  We have 5 zones, we have 5 valves, .... one valve on each zone.  The radiators have a manual feed valve feeding the steam up top and a bottom drain at the other end followed by a thermostatic condensate valve.  Condensate then returned to boiler via condensate return pump. Two pipe steam system.



The pic of the low low emergency control looks similar but not the exact same manufacture.

jpf321

i edited...while you types ...

when was the last time you "probe"was cleaned? and don't use teflon on the probe threads according to the install instructions .. the threads need to make a contact with the boiler metal for the proper conductivity and teflon sometimes screws up that contact. 

BAB

Boiler cut off

Boiler maintenance tech in here 10/2010.  Very thorough guys (his last name is Clark). I do not remember if he pulled the probe apart, .... I can call him & get him in on this whole mess.  It would be a nice clean solution, would prefer it to pulling pipe apart.  That big pipe wrench gets heavier each year. 

BAB

Boiler cut off

Wait a min.  The emergency probe works. If anything it works too good.  Or are you suggesting that a dirty or defective probe might get too sensitive?  It activates too quickly?  .... every now & then.  

jpf321

that's about as far as I can take it ...

If you aren't actually losing water visibly or invisibly (underground)

And you're condensate pump is pumping

And your water level is fairly steady

And you #47 is working properly (albeit adding some amount now and again)

And your 2-pipe is returning water independent of the zone valves blocking (even though the beginning of this thread you were saying that your 6" main was pouring water BACK INTO boiler) .. so as long as your 6" that is flowing water BACK INTO is never zone-valve blocked, you are OK...if it is ever blocked, how does that water, that you thought was enough to cause a bouncing waterline, get back to the boiler?

And it's definitely a water thing and not a pressure thing ..



I'm outta ideas .. but you do state that the thing that LOCKS the boiler out is the little LOW LOW Probe .. which may or may not have been cleaned .. and although I'm not sure if the actual electronics ever go bad, it is possible that the electronics in that unit have for some reason gone bad .. I hope that the solution lies someone in that 1cubic foot area... as that would be an easy fix.

jpf321

i dunno what...

happens with a dirty probe .. as far as I know .. the probe needs to make contact with water + boiler metal .. if the probe is dirty and for whatever reason slimy or scaled or something that is NON-CONDUCTIVE with the water, then it would lose the circuit and register as NO WATER .. EVEN THOUGH THERE IS PLENTY. But I don't know what environment within the boiler if any would cause a false-positive .. but if the probe loses conductive circuit (between water and boiler metal), it will trip the unit. this may include if the probe was so dirty that it was sometimes non-conductive with the water. 

BAB

boiler cut off

I started this thread by incorrectly assuming that the returning condensate was causing bouncing, .... therefore tripping my emergency boiler shut off probe.  You guys immediately educated me on the fact that a one inch bounce is not enough to screw up my Series #47 and/or also my low low level probe (emergency boiler shut off probe).  Over the next several days I will skim & more closely investigate the emergency boiler shut off probe.  Thanks for your comments.

jpf321

right but ...

you then also said that your condensate doesn't return that way and will never be locked out by zone valves by alluding to the fact that you have a 2-pipe system where the water ALWAYS returns on the far side of the zone valves ... if you have water that is returning back through the 6" header, is there a possibility that that water is being locked out by zone valves?



keep us posted, gnight.

Enreynolds

Scaled up probe

We had a similar situation with a Smith GB-300 that the former owner had neglected nearly to death.  Occasionally the low water cutout would trip for no apparent reason.  I finally pulled the probe and found the well all gunked up and the probe itself with a layer of scale covering it.  With some very delicate scraping so as to not damage the probe, I was able to get it working reliably.  It has served well for the last 4 years (I have purchased a spare replacement for the inevitable midnight 'No Heat' call).  So maybe give the probe a once over.

BAB

Boiler cut off

I did a quick schematic to show the system.  When four zones are closed (heat demand satisfied) and Zone # 5 is at the end of it's heating cycle we do witness very busy low/low boiler level action.  The four zones closed near the main now trap and hold steam.  The trapped condensing steam causes some back-flow of condensate within the main.  The steam main discharge is still feeding steam to Zone #5.  The Zone #5 modulating control valve is at the end of the heating cycle and therefore almost closed.  The boiler is really pushing steam out at a full clip at this time.  The boiler water is usually below the mid range, the boiler has been running none stop for 15 - 20 min and at peak performance mode.  The steam has to make a 200' plus run to feed Zone #5 and the condensate seems to take forever to fill the condensate return tank to kick on the boiler feed pump.  Just when you are convinced the sight gauge level drop is going to trip the boiler emergency shut off, .... instead the # 47 feed turns on , and/or the # 47 turns the boiler off then on again as the #47 adds more fresh water, or the condensate return/boiler feed pump kicks on returning the level to the mid to low mid range on the sight gauge.  After the boiler feed pump returns water level we do not see the low/low condition again for 3-7 min.  On a cold cold day this infrequent condition happens 2 - 3 times a day.  The fresh water that has to be added might total out at 2 -3 coffee cups.  The on/off water feed action is fast and rare.



All the above may be exciting to watch but everything does what is supposed to do when it is supposed to do it.  The devices & systems work, .... except every once and a while some thing triggers that low/low level probe shutting the boiler down requiring a manual reset.

Long Beach Ed

Zone valves on one pipe steam

Zone valves are notorious for causing problems.  Remember that when a zone closes, it may cause vacuum or trap condensate.  When we have problems with them we often install bleeders or a small 1/2" pipe around them.  Vacuum breakers can also solve problems.  



We faced a five zone church job that was out doing all the same things and these remedies got it working right.

jpf321

zone valves trapping condensate???

I still posit that your zone valves may be trapping condensate which isn't released until the zone calls again. Especially if those zone valves are vertically oriented at the end of a significant riser length. perhaps it's not an awful lot of condensate, but between them, it would be several coffee cups full. If you really feel like swinging your wrench, you can/should drip the condensate just after the zone valves to a wet return.



As a test, if you have ability, reopen a zone valve during cycle but after it has been closed a few minutes...you can see if you are in hammer city as the steam picks up the water that had been trapped behind the closed valve. Currently you probably reopen during a non-steam condition.



My guess is that the system wasn't originally designed with ZVs and they were added sometime later.



I would not worry about the condensate on the closed supply side of the ZV. That should, as you originally mentioned, drop back into the boiler via the header.



i did have 1 questions late last night .. is the Low Water problem you are now experiencing a new problem or old problem?



 

BAB

boiler cut off

The emergency cut off probe has always been a problem.  We never had one on the older boiler that we overheated.  When the pros said we had to have one that was that.  We compensate by riding the water level very, very high so the low level probe trips less often.  It took a season or so to zero in on the problem.



I will visit uponest the boiler in an hour or so.  Always worry going into work that it shut down again.



My schematic is not to scale or a real view, .... all the Honewell/Jamesbury motorized control valves are mount horizontally, none are vertical.  After the valve we have many vertical condensate drip legs with thermostat traps to keep the sub mains drained of condensate.

jpf321

points well taken ...

but just to clarify, he's got 2-pipe. but I still think he needs some bleeders. 

BAB

Boiler cut off

Are drip legs = bleeders?  Notice I edited one of my above posts.



>>>>My schematic is not to scale or a real view, .... all the

Honewell/Jamesbury motorized control valves are mounted horizontally, none

are vertical.  After the valve we have many vertical condensate drip

legs with thermostat traps to keep the sub mains drained of condensate.

jpf321

ok .. then ...

that leaves us with the potentially faulty LOW LOW Water Probe. fingers-crossed. 

BAB

Boiler cut off

Boiler ran the whole night with no cut off.  Yesterday we brought the operating boiler water level to middle gauge to have system run as it should.  It cycled from upper middle down to mid level most of the time.  On heavy/long demand it would approach low/low & only added water rarely for short spurts.  #47 cut offs very rare but always turned boiler back on correctly.



This morning we skimmed the boiler water.  First 5 -10 seconds (est) of skimming showed black colored water.  We stopped draining to catch a sample but we blew that chance.  It happened too fast & that was all there was.  Rest of skimming was fairly clear to clear water, ... not crystal clear but fairly clear.  We skimmed & played with it for 1/2 hour.  Except for that 1/3 - 1/2 gallon of black at the very beginning we had nothing but clear water.



Model #550 Safgard Low Water Cut-Off, by Hydrolevel Company, New Haven, CT.  Will pull to inspect probe after I clear a few alligators biting my **** on other (not boiler) matters.  Boiler was installed new in November, 2005.  #550 was installed new at that time also.

BAB

Boiler cut off

Pulled probe.  Surface had some oxidation on outside diameter cylindrical surface.  Cylindrical flat butt end had 15 -25% of the oxidation starting to become scale/crust buildup.  Nothing I would have worried about except for your suggestions and the factory installation comments:



MAINTENANCE

To ensure optimum performance, inspect probe annually.

Clean any scale or build-up from the probe using a scouring

pad or steel wool. Re-install the probe and test control

in accordance with the Operating Instructions.



The main probe became a shinny stainless steel looking finish after we cleaned.  The brass male nipple mount end had some pipe dope on the outer side only.  First 1-2 threads were definitely metal to metal.  We wire brushed lick hell & cleaned the threads real good for definite metal to metal contact.  Reinstalled with no pipe dope and no Teflon tape.



We will watch closely for the next several days & hope you are right.  Either way we will be back at you with the results.  I tried to take pictures today but it looks like someone sat on our digital camera & it is busted.  Will try again soon



Thanks for the comments & especially for not holding back.

jpf321

I see....

You found the manual

http://www.hydrolevel.com/pages/pdf_files/550_650_750_opt.pdf



read the section about nuisance lockouts and see if it applies

BAB

Boiler cut off

Per your suggestion I read the following section of the operating instructions.



SECONDARY CUT-OFF WITH CRITICAL DIFFERENTIAL:

On some installations it may be necessary to mount the secondary cut-off at a

level in close proximity to the primary cut-off level. In these situations, when

the primary low water cut-off shuts down the boiler, the water line can settle

below the secondary cut-off causing nuisance lockouts. The wiring diagram at

the right is designed to prevent these lockouts. NOTE: This wiring method can

only be used if the power supply from the primary cut-off is 120 VAC.



In our case when the turned off boiler is inspected, after an emergency low low level activated cut off, .... the boiler water level always has been at the proper midway level & set to run again.  I have no field observations of a "... water line .... settling below the secondary cut off ...".  Also, we are already accomplishing the primary & secondary activity concept by the use of the Series #47 coupled with the #550.  They are suggesting a fail/safe or a redundancy approach on the emergency shut off.  I realize that we may have a "nuisance lockout".  But I see no proof of it yet.  If the boiler is shut down in the next 48 hours I would probably further examine my condensate return piping for blockages rather than move on a electrical fix for what may be a physical/mechanical glitch.



I like your earlier suggestions that we just have a dirty probe or slim/scum/oil on the boiler water, ... or both.  We checked boiler operation at 10 pm tonight and all was OK.  I'm extremely glad that you immediately killed, or squashed, my drain piping approach at the very beginning of this thread.

jpf321

thanks ..

for keeping us well informed. I was at the theater tonight so I couldn't write much during intermission .. but I'm glad you pulled the probe and cleaned it well. i'll be standing by for more info. hopefully things move forward .. btw, you never mentioned if this was a new problem or an old recurring problem. at least I don't remember you mentioning it. 

jpf321

not sure ...

but I was just reading in TLAOSH .. about motorized zone valves and how when closing them your Dimension A becomes a Dimension B .. since you have lost the pressure assistance of steam .. perhaps this has something to do with things .. just something I wanted to throw out there and have you and others ponder ..



apparently Dimension "A" relies on water stacking + steam pressure .. however, Dimension "B" is ONLY water stacking without steam pressure .. so in order to get the water back into the boiler you need to have more water stacking height than is you had the steam pressure behind it .. without this height, the water cannot overcome the pressure within the boiler ..



AHHHH .... nevermind, you have a condensate pump (presumably properly vented to the atmosphere correct???) ... well it was worth a try ..

BAB

Boiler Cut Off

I understand your concern on the zone valves.  We did have weird things happen when we had the original boiler and ran the system with the vacuum pump.  I remember trouble shooting a radiator and the steam was coming in from the wrong end, ... through the defective condensate thermostatic trap!  Another time I thought we were pulling a perfect vacuum from our vacuum pump when in fact that specific heating zone had it's zone value closed and after the boiler shut off the zone went into vacuum mode.



As the pump impeller became cavitated we started to run the system not vacuum but 3 -5 psi, low pressure steam.  We still had unexplainable things that plagued the system.  The zone valves were often suspect.  We did not intentionally redesign anything but as we started to add Gorton air vents, re-pipe condensate drip legs to include an air vent , and air vent condensate line where ever safe & possible the system gradually worked & heated at lower and lower pressures.  Our pressurestat is still set at 3 psi whereas our system operating pressures are typically 3-4 oz per sq in.  We have not run the system in excess of 1 psi except that one shut zone valve incident last year when the system reached 3 psi shut off pressure.  So some of the complicated things that you suggest with zone valves may happen on other systems, ... our system is loose as a goose & technically under true heating loads very easy to trouble shoot.



Yes, we have a condensate return pump and it is vented to atmosphere.  Boiler did not run much today but I like to think we did the right solutions.