Steamed up over Steam Boiler Short Cycling

Red_Fred · December 2012

Tired of Steam, I have spent so much time studying and making changes to get my old boiler, and now my new boiler, working correctly that I wish I had ripped out the steam and installed hot water baseboard heating, with 3 nice zones. My old 30 year boiler rusted though so I recently had it replaced with a new boiler. Now the new boiler short cycles endlessly. 

Details: 1 pipe system. 2” pipe. 45 to 50 ft main.

Small 1930 2 story house with 8 radiators.

Basement baseboard heat running of bottom of boiler.

Gorton 1 on main (soon to replace with a 2)

Honeywell thermostat Round HC Thermostat, delay set to longest possible (1.2?)

Gas boiler. Input: 138,000 btu

Output: 113,000 btu

Honeywell Pressertroll

Cast Iron pipe connections on header and Hartford loop.

Pipes have insulation but I need more by header. 

Standard useless 0 to 30 gauge

 

Set thermostat to 65. Boiler runs for 20 min shuts off. Then another 20, then another 20.

Then 10, 10, 5,3, 3, 2 ,2 and it continues to run for 2 minutes the of for 1 then on for 2 for about another hour. I get tired of it so I throw the master switch. Temperature finally gets to 65. Cannot get it much higher.

There is no skim valve so I drained and filled the boiler 6 times over an hour. I can’t take the pressure relief valve off to add a cleaner easily because it is against the boiler cabinet. If needed can I pour cleaner in the tap for the main valve?

Replaced all valves on radiators based on chart. 5,6,C (Upstairs bedroom radiator still went off like a Tea kettle one night at 4 AM)

One test: Removed main valve until system filled with steam. Still short cycled.

Removed basement thermostat

Removed main thermostat and connected the wires to make boiler run constant. Boiler just continued to short cycle.

Can I return a 4 week old boiler? Otherwise I may fix it with a sledge hammer.

jim s_2 · December 2012

How about some pictures

They would certainly help.

nicholas bonham-carter · December 2012

Short-cycling problem

Short-cycling is usually caused by lack of main venting, in addition to over-sizing.

Whatu is your pressure on a good low-pressure gauge (0-3 psi, gauge store.com)?

Have you timed the steam to the main vent from start of cycle? Well vented systems will have the main vent closing in a few minutes, and then steam inside the rads shortly after.

When the boiler was replaced, how was it chosen?--NBC

icesailor · December 2012

F***ing Magic:

The boiler and system are not possessed by El Diablo. Just because you read all the books and study all the information that you can find here and on the Internet, doesn't put you in a position to become an expert in hydronics. And I don't consider myself any form of an expert. Especially on steam.

The boiler/system had problems had problems before it had the boiler change. Some of us would consider that there were problems before that were carried over into the new boiler.

The new boiler has never been skimmed. You didn't say what brand of boiler but you railed about the PR valve being too close to the "Cabinet". They're ALL too close. Somehow, we pro's get them out. If no where else, you could take out the ell, replace it with a tee, skim through the run and out the PR valve in the branch of the tee. Filling and draining the boiler 8 times just covers the insides of the boiler with oils as the water level drops and rises 8 times.

If a radiator went off like a tea kettle in the middle of the night, that's not a boiler problem, it is a system problem.

You have a basement baseboard loop. That isn't steam, it must be hot water. So you are maintaining hot water in the boiler or not. But how is that water being separated from the steam return. How is it controlled?

You sound like you have a bigger control issue. The higher the pressure, the more short cycling you may get. You can't tell much with a 0# to 30# gauge. You need a 5# gauge.

Did you do a heat loss in the building by calculating the EDR of the radiators or did you just replace the boiler with a like kind that was over-sized already?

You have other issues.

You need to post pictures of the boiler and near boiler piping.

BobC · December 2012

Pressure and system EDR

What pressure is the boiler operating at and what is the pressuretrol set to?If it's higher than 2 PSI it just makes things worse. Is the boiler always shuting down on pressure or because the bouncing waterline is tripping the LWCO? That boiler is supplying 470 sq ft of steam, what is the EDR of all your radiators?

Most boilers these days have a dedicated skim port tapping, get the installer to remove the plug and install a pipe nipple and a full port valve so you can skim the boiler. A new boiler will NEVER work right till it's skimmed.

Please post some pictures so we can see what your dealing with.

Bob

ChrisJ · December 2012

Cyclgaurd

Don't think anyone else mentioned it but the Cyclegaurd LWCO also slows things up by cycling the burner for almost no reason other than to check for foaming. If I had one I'd replace it with a standard LWCO.

You said a radiator went off like a tea kettle. This sounds like the boiler is oversized to me. You said you spent a lot of time learning about steam, why would you have an oversized boiler installed?

None of my radiators would, or could go off like a tea kettle even if the boiler ran for 5 hours due to the fact the radiators condense the steam nearly as fast as its made.

Pressure relief valve should be plumbed in copper with a union for easy removal as these do leak from time to time and must be replaced. The stem on the pressure relief also must be vertical, if its installed horizontal someone didn't read the tag.

Jamie Hall · December 2012

Fools walk in

where angels fear to tread.

You need to take a deep breath and start back at the beginning.

First how does the radiation (your eight radiators) compare with your building heat loss? I ask because you say you can just barely get up to 65 -- and under radiated is one possible reason.

Second, how does the boiler size compare to the radiation? You don't mention the total EDR of the radiators, but if they are kind of average sized I'd bet that that boiler is at least 50% oversized, if not more. That will cause short cycling, no matter what else is wrong (as ChrisJ noted, a properly sized boiler will cycle -- on pressure -- only on very long recovery runs, if at all). If in fact the boiler is seriously oversized, you might be able to down fire it -- but it is more likely that the only cure would be to replace it with one which is sized properly.

I hope the basement baseboard heat is running off a heat exchanger and not using straight boiler water...

Then you might want to check that your controls are working the way they should. Your maximum pressure should be 2 psi -- achievable with a Pressuretrol, but only with care. And check that the thermostat is really working right; if it is one of the older mercury ones, is it level? Seems obvious, but...

Then there is the whole clean the boiler thng.

Problem is, you seem to have an array of problems, and they interact...

Red_Fred · December 2012

Radiator details

Thanks all, (this is a great web site)

History: House had a 25 year old boiler when I moved in and it was short cycling. So I replaced all the radiator valves, gas valve, and thermocouple and it worked well. Then it cracked but I managed to get 2 more seasons out of it. I was debating to change to hydronic baseboard but to much happened this year. Next thing I know it was Thanksgiving, colder out, and not time to do it. The wife complained so I called a plumber to install the new boiler. (I successfully installed a hydronic baseboard system in the last house we renovated. Before we occupied the house the old system shut down in a blizzard and all the pipes in the house froze… but that’s another story.)

Radiators:

They are painted with wood covers over them. They are Thatcher / American Rad and 2 Sunrad recessed into the wall. I lined the recess in the wall with sheet metal.

(Full calculations in table in next post)

EDR 231 x 240 = 55,400 x 1.33 = 73,735

Boiler is a Crown BSI138

Gas boiler. Input: 138,000 btu

Output: 113,000 btu

So if the boiler is two large can it be downsized?

Is it save to run? I fear what it does while I am not home and when the weather gets colder.

Right now I just shut it off for a few hours and then turn it on again rather than letting the thermostat do that.

Out of 4 plumbers I called this was the only one willing to do cast pipe for the header, all the others told me it was old fashioned, out dated, and they don’t do it that way anymore.

( I will try to get some pictures up)

Red_Fred · December 2012

Prevous Post did not like the table..

Prevous Post did not like the table..

                    Vent Height Sections Columns EDR        EDR*Sec

Living  1       5       26          9               5          3.5           31.5

Living  2        5       26          9               5           3.5         31.5

Dinning         6      26          13            5           3.5          45.5

Kitchen         6       20            7              3           2.25        15.75 Sunrad



2n fl

Bed Small     5       26          7                5          3.5            24.5

Bed Medium 6       26        10                5         3.5               35

Bed Master   C      26         9                  5         3.5             31.5

Bathroom      C     20         7                  3         2.25            15.75

TOTAL                                                                                     231

Also it soes have a Cycle Guard and the water bounces about 3/4 \inch up and down.

ChrisJ · December 2012

Too big

"Out of 4 plumbers I called this was the only one willing to do cast pipe for the header, all the others told me it was old fashioned, out dated, and they don’t do it that way anymore.

"

Yea, so is taking pride in your work.

As a homeowner I do not know how much you can downfire that boiler, but I've got a feeling you might be in luck. Though I have a feeling it would need to have at least one burner tube removed and this MUST be done by a pro. They most likely would have to contact the manufacture to see just how far they can go. Sadly the end result is still a system which burns more fuel than necessary as it still has to heat all of that water which will take more time than the proper size boiler.

Its a shame too because the Crown BSI103S is a FAR better match to your system coming in at 85,000 btus.and 267SQFT of EDR.

Hopefully some pros can comment and give you some advice on what your next step is.

ChrisJ · December 2012

vents

I would leave the cyclegaurd alone for now as its not technically wrong and you really don't want to over complicate things at this point.

What vents are you using on all of the radiators and what main vents do you have?

Faster radiator venting can help get the radiators condensing steam to give them a running start. Also main venting must be as fast as absolutely possible.

I used mostly Gorton #6s on my neighbors radiators and it helped a huge amount. Gorton Cs or even Ds can also help but they are really fast and may cause other problems if pipes arn't pitched just right.

I am not familiar with the radiators you have so I may be wrong, but I am typically against radiator covers as they usually reduce the radiators ability to get rid of heat.

BobC · December 2012

install a skim port

It looks like the boiler is about 50% oversized. That is not optimal but it's not the end of the world either. It's going to cycle on and off because it's opversized but you should be able to get good heat out of that setup without much noise.

If your not getting good heat it could be venting, dirty boiler water or a number of other issues. Are you getting banging in the pipes or is the water in the gauge glass bouncing up and down a lot?

Dowfiring an oil boiler is possible but not by more than 10-15%, if it's gas you pretty much have to live with it. The fact that you don't have a skim port makes me think the boiler was never skimmed, new boilers HAVE TO BE SKIMMED if you want them to work right. Get the installer to install a skim port and a full bore valve on it so it can be skimmed.

Bob

ChrisJ · December 2012

skimming

I'm sorry I completely missed that.

As BobC said skimming is a absolute must. It took me 7 times over a period of 1 year to get my boiler clean and each of those 7 times easily took 2-4 hours.

BobC · December 2012

I followed your lead

with the steam master tablets after skimming my new Smith G8 four times. I gave it the 4 tablet blast and then drained it all out after letting it steam for 20 minutes. I popped one tablet in and refilled the boiler and my PH was about 9.5.

I pulled a little water out of the drain yesterday and was sparkling clean -great stuff.

Bob

Red_Fred · December 2012

Venting and skimming

Vents: I put all new Maid-O-Mist valves on the radiators. This definetly helped. I figured if I got the banace right I may upgrade to Gorton valves in a year or two. I pu the Cs on the rads on 2nd floor farthest away.

As for the main it has a Gorton #1. To test I removed the valve completely to let the steam come through. When the steam blasted out of the fitting I screwed the # 1 back on. The system heated faster so I purchased a Gorton #2 to put on an antler with the gorton #1 that I have already. Alos the main valve is of the 90 before dropping to the Hartford loop.

Skimming: I will need to get a vavle installed, believe there is 1 port left on the top left. In the mean time I did a really slow drain the boiler again today. Got a lot more brown water out.

Is it safe to let the boiler run and keep short cycling? Other than the fuel cost and the fact ti is really annoying.

Thanks Chris J and Bob C

Red_Fred · December 2012

PIctures

Pictures

Red_Fred · December 2012

Baseboard and Heat lose

Baseboard: It runs direct off the boiler. Starts at the Hartford loop and returns via the cleanout on the other side of the boiler. Straight boiler water. This was installed before I purchased the house when the basement was refinished about 20 years ago. I don’t use it much, always thought the thermostats were fighting each other. On current boiler I completely disconnected the thermostat in basement to take the basement loop out of the equation. Boiler still short cycles.

Heat Loose: House was built in 1929, stucco, and plaster, no insulation in 75% of walls. Attic insulated. I installed all new 2 pain replacement windows, and new tight doors which helped a lot. Insulated sill around foundation and was able to bring basement up from 55 max to almost 70 max. Previous boiler fired less after the upgrades. Rest of house still tends to max out at 65 maybe 68. 68 is nice but once in a while it is tuff on 0 degree nights.

Comment about PR valve being too close to the "Cabinet”, I can get it off if I cut the overflow pipe and wrench it off. It’s just that if I want to unscrew it, drop some boiler cleaner in, and screw it back on, its not so easy…so how do I get boiler cleaner in now?

I am just frustrated with steam because I have spent more time with steam than hydronic baseboard to keep systems running.

Thanks icesailer and Jamie Hall

Paul48 · December 2012

Way Big!

That boiler is rated for 354 sqft of steam.

ttekushan_3 · December 2012

poor heat delivery

What do those wood radiator covers look like?

I'm getting that you're having trouble heating the house but also have short cycling. The oversize boiler will cause short cycling on longer run times.

Are those run times long because of the radiator covers?

There's a whole art and science to those things.

I've solved poor heat troubles for clients by redesigning or modifying poorly designed radiator covers.

Subtleties of their design can increase, leave unchanged, decrease, or devastatingly decrease radiator output.

A picture of a typical cover would be helpful.

BobC · December 2012

Annoying but safe

The short cycling is annoying but poses no safety issue.

Terry is right about radiator covers being variable depending on their design, try romoving one cover and see what a difference it makes in the heat delivery of that one radiator.

Bob

Dave in QCA · December 2012

Hydronic Baseboard loop

Since your boiler is over-sized, it obviously has plenty of capacity to run the hot water loop that is connected to it. If this loop is running at the same time that the boiler is making steam, it will reduce the amount of short cycling. The difference that it will make will depend on the size of the hot water loop. Also, since you are having a hard time heating the house, extra heat coming from that loop might help in that regard too.

I agree with all of the rest of the ideas posted, especially analyzing the effect that your radiator covers might be having on impeding the heat coming into your your living space. Keep in mind, if they are impeding the ability of the radiator to give off heat, they are also reducing the amount of steam that the radiator can condense, and thus adding to your short cycling.

Please take some pictures and post them. Make sure that each picture file has a file name different from the rest and that you hold the camera in the normal orientation. If you hold the camera in the vertical orientation, please edit and save the picture file prior to uploading.

Jamie Hall · December 2012

Just something else to check...

Do the radiators get hot uniformly across when the boiler starts to shut off on pressure? And stay that way? I ask because sometimes some vents will close on steam, OK, but then, if the pressure never drops low enough, will stay closed, steam or no steam -- and if the vent can't open again, you won't get much more steam into the radiator and will get very poor heating.

It's another thing to check and, if you find that that is the case, check your pressures again -- the system should shut off at no more than 2 psi, and drop to preferably no more than 1 psi before kicking back on. This is right at the bottom limit of a pressuretrol, though, so be a little cautious about trying to set it down low enough.

As others have said, that boiler is way too big. I am not a boiler installer or technician, so I couldn't say if it could be downfired enough to match the load on it, but if not you will either have to live with the short cycling -- or get a new boiler (yeah, I know, ouch).

Mark N · December 2012

Thermostat

According to the original post the anticipator is set to 1.2a. On page 16 of the install manual they recommend .2a. I have a Burnham Independence which is very similar to your boiler. My boiler is 1 size smaller than yours and I have 7 rads (260 sqft EDR) in my house and also a FHW loop that heats 2 rooms and my entrance way. My boiler runs about 20 minutes on a call for heat and easily keeps the house at 70. I ditched my rad covers about 4 years ago after I discovered they caused the boiler to runs 10 to 15 minutes longer on a call for heat to satisfy the Tstat. It seems you have adequate rad venting and you will have more than adequate main venting once you add the Gorton#2. Time how long it takes for the header to get hot after the boiler turns on. Then how long it takes for the main to heat all the way to the vent. After looking at the manual I see that it shows you have a tapping for a skim port. Get one installed and skim until the oil is all gone.

icesailor · December 2012

Heat anticipaters:

Are you sure that the instructions for your boiler says to set the heat anticipator to 2 (two) amps? He has it set for 1.2 amps. That is the maximum setting for a Honeywell T87F thermostat. Taco 571 wax motor zone valves are high amp valves and they only need .9 amps. If you had a boiler with controls that required 2 (two) amps, the heat anticipator would be instantly burned out even if set at 1.2. I think that the proper setting is .02 amps. The only proper way to tell is with an Amp Mate wired through the thermostat when it isn't calling. Futzing with the heat anticipator and setting it to settings way to high can have interesting consequences. Though not as bad as having a .9 amp dray and the heat anticipator set at .04. Setting the anticipator to "run longer" doesn't always give the results expected.

As usual, there are some really great suggestions here.

Listen up folks.

ChrisJ · December 2012

1.2A

Icesailor, I thought with a T87 having the anticipator set to 1.2A essentially disabled it making no current run through it?

When I had my T87 the way I adjusted it was by simply using my fluke DMM as an ammeter wired in series with the tstat.

Red_Fred · December 2012

Radiator Covers:

I have been asked about the radiator covers. I have 6 radiators with wood enclosures. I like to make furniture so I made the enclosures myself. 5 are made of pine. The dining room cover is made of oak that was salvaged from an old bookcase. The dining room cover is my favorite. You may notice some shims under the covers since the old oak floors are not even.

All radiator covers are 29” high, 2.5 inches higher than the radiator.

Width of covers are 2 inches wider than the radiators on each side, including floor valve.

Radiator tops are 13.5 to 14.5 inches wide from wall to front.

The radiators are tilted to drain. The first floor radiators have flaking silver paint and the second floor radiators have silver paint with one or 2 coats of wall paint over them. The painting had been done by previous owners. So they are really ugly and why I love the covers. I should remove them and blast the paint of them but they are heavy.

The bathroom and kitchen Sunrad radiators I removed, stripped, and spray painted the front and sides an antique bronze with Krylon paint. I added insulation, caulked recess, and then lined the wall recess with sheet metal to reflect the heat out.

Mark N · December 2012

Thermostat

It says .2 amps or 0.2amps.

Jamie Hall · December 2012

Nothing wrong with those covers --

They shouoldn't be causing a real problem. A little bit, maybe -- but not enough to account for the inability to get the house much over 68 with the boiler running and running.

How about the heating across question?

ChrisJ · December 2012

Covers

Jamie are you sure? Every one of them has a solid stop which would completely stop the draft up through the radiator eliminating most of the convention resulting in only radiation. no?

Mark N · December 2012

Rad Covers

Very nice looking covers. Maybe just add some vents in the cover to let the heat out. The rad covers I had had solid tops and they reduced the heat output by like 30%

Jamie Hall · December 2012

Well...

It's mostly just my opinion -- although I did see somewhere a study on radiator covers which seemed to suggest that if there was clearance over the top the air would convect out OK. Maybe some one of our more organised folks can find it... maybe it would be better if the tops were open, perhaps, but air is, if anything, even cleverer than steam at finding a way out!

I find it hard to believe that that's the reason why he can't get much above 68, though, since it isn't really even that cold out yet. Seems to me that there's got to be something else going on we haven't seen yet.

Mark N · December 2012

Rad Covers

I agree with Jamie even when I had the covers on the rads I was to keep the house at 70.

ChrisJ · December 2012

covers

Jamie, I tend to agree on that.

I would assume the reason he can't get past 68F on a cold day is a combination of venting and dirty water.

Hmm. Maid-O-Mist vents were mentioned but not which specific sizes? If they are all #4s assuming they are numbed like Grton's that would certainly explain a lot.

icesailor · December 2012

Amps:

Sorry. I missed the decimal point. .2 amps would be correct.

Paul48 · December 2012

Delaying the inevitable

Running the hydronic zone at the same time, may delay the production of steam, but once that over-sized boiler starts making steam, the boiler will short cycle like it wasn't there at all. My opinion

Jamie Hall · December 2012

Ha! Found it!

http://www.heatinghelp.com/article/158/Radiators/1537/Radiator-Enclosures

As Dan says -- sometimes it pays to wander off the wall.

icesailor · December 2012

Thermostat anticipation/Disabled:

Not really.

The "anticipator" with the adjuster is like a rheostat/dimmer on a light switch. It bleeds off amperage through the "dimmer" because the current goes through and dumps heat. The heat is absorbed by the bi-metallic coiled spring that holds the Mercury vial.

When you have a thermostat set at .2, and have a Taco 572 wax motor valve that draws .9 amps, It will need to dump off a lot of heat. The call/complaint will be that a customer will call with a complain that the boiler starts in the middle of the night and runs for 15 seconds and shuts off. A few minutes later, the burner starts again and runs for 2+ minutes and shuts off. A few minutes later, it starts again and keeps running.

As the temperature drops in the room, the thermostat responds. But it hasn't dropped enough for the anticipater and the excess heat/current to overcome the drop in temperature. The next cycle starts again but the temperature has dropped more. But not enough. On the third try, the temperature in the room has dropped enough that the heat anticipator doesn't send out enough heat to overcome the drop in temperature. If you have a tribe of zone valves improperly set, the burner will be starting and stopping all night long. Setting them all the way over to 1.2 amps resolves all problems. Back years ago, boilers were shipped with a thermostat. A cheap Honeywell T884 or something like that. It had no base plate and could only be set to .8 amps. Some would use that one and t-87's on a system. The anticipator would burn out on the thermostat. And they spent their lifetime turning the boiler on and off.

ttekushan_3 · December 2012

Those radiator covers don't look particularly obstructive.

Although they are closed on top, I'm not sure that they can be causing such severe trouble heating the space.

As mentioned above, you might slip one away from the radiator just to see what happens. If it does the trick, then we can talk about aesthetically pleasing ways of modifying the existing covers for better heat transfer.

This is also a good time to confirm that the radiators do, in fact, get completely hot, as Jamie points out. Steam that travels too fast that closes the vent and pressure that holds it closed can cause a radiator to partially heat despite more than adequate steam supply.

I wonder if this is one of those instances where a vent with a snap acting float like the hoffman might be a good choice. Especially if you don't mind a ssssssst *clink* sound occasionally.

But I would start with the cover removal experiment and confirm complete saturation of the radiator first.

ChrisJ · December 2012

Hoffman

I would advise against Hoffmans, at least the 1As.

I have nothing but problems with them getting water stuck in the orifice which causes the radiator to stop heating.

At least one other member here has the same problems and we both feel its a defect in the design as they changed somewhat recently.

I'd go with Gorton.

Red_Fred · December 2012

Should Baseboard Loop be part of steam boiler sizing?

RADIATORS: I never seemed to have a problem with the covers prior. Main issue is new boiler short cycling. Main fear is it is too large and something I cannot adjust. Radiators are all heated. Large dining room (13x5 sections) is 160 deg at top valve side, 110 at bottom at floor below vent. Upstairs farthest away is 140 at top valve side and 100 at bottom below the vent.

BASEBOARD LOOP: Dave in QCA's idea about the baseboard makes me wonder. The heat for the baseboard is not part of the equation for sizing my boiler; it is just sized on the steam radiators. I have 28 ft of slant fin and 55ft of insulated copper pipe in the loop. I spend a lot of time in the finished basement and if the heat rises to the rest of the house it would be nice to leave this on. If my worst case scenario is that the boiler is oversized (Agh!) perhaps the baseboard brings it closer to the right size? Would letting the basement heat circulate stop the short cycling?

I just don’t understand why if the thermostat is set to 68, and the temp reaches 68. Why does the boiler keep running on and off for another 30 or more minutes? Obviously the steam has reached the radiators and heated the house. No need for steam, no need to worry about the pressures in system. The boiler should just shut off. Job done.

nicholas bonham-carter · December 2012

Short-cycling

Maybe the thermostat, or its locationt is the culprit. Is it on a cold wall?

You can never be sure that the thermostat thermometer, and mechanism are reacting to, or reading the same temperature. The old mercury thermostats must be mounted level in order for the temperature setting to be accurate.

Get a Taylor indoor/outdoor thermometer, and see what the temperature is next to the thermostat, and then turn the correction screw in the thermostat thermometer accordingly.

Some walls which join with an outside wall can pick up stray currents of cold air and cool down a thermostat. First step is check the thermostat.--NBC

Steamed up over Steam Boiler Short Cycling

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