vaporstat: on, off, on, off

Steven Todd

Hello. I have a single-pipe steam system (single family home) with a new Honeywell vaporstat (a beautiful thing; main=10oz and subtractive diff=6oz). Thermostat (whiterodgers) calls for heat, boiler starts, mains heat, main vents get hot & close, rads get hot & vents close (takes about 35 minutes). That's fine.

Pressure builds and vaporstat turns off boiler; 30 seconds later, boiler turns back on (pressure has dropped); 90 seconds later, boiler vaporstat turns off boiler (pressure has built back up). This pattern continues until thermostat is satisfied (about 30 minutes later, to bring the house from 62* to 67*).

I've gone through The Lost Art but I can't figure out if this 30-second/90-second pattern is normal. It seems like the system would like to coast for a while, with the hot rads radiating.

Thank you.

Steamhead

Try

raising the Main to 12 ounces, and the Differential to 8.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

gerry gill

well, okay..think about this

I know i'm gonna get jumped on for this, but so what...if the boiler is sized to the radiation and a third added for piping, then when the pipe is hot and not condensing much anymore, you effectively have a boiler oversized by one third, don't you, nod your head yes...if the boiler was oversized by a third (in essence), its going to build up pressure, isn't it....you can either downfire the boiler a bit or install a two stage gas valve that will drop out the extra third once the end of the main gets hot..if your a homeowner you will need a pro for this- if your a pro you will need your combustion analyzer and manometer for this, which you knew already cause your a pro..we have boilers running both ways and they mimic thier coal boiler predecessors very well..what you want, (in theory) is to have the system cycle on thermostat not pressure switch..what usually happens is its most achievable on spring/fall days and not so achievable on really cold days..

Steven Todd

Thank you.

Thank you Steamhead, I'll give those settings a try.
Steve

matt_31

I am a homeowner.....

I have a similar circumstance with a pressuretrol where after reading this site I removed the pressuretrol and cleaned the pigtail (which was completely clogged) and then boiled the mains vents and all radiator vents in vinegar to clean them. the differential on the pressuretrol is set at 1.5lbs

Now the system will fire the boiler and run till about 5-10min after all the vents close and the radiators are all hot and then shut off from the pressuretrol even though the thermostat still is calling for heat. About 10-15 min later I will hear one of the vents open and start letting air in/out? and then the boiler will fire again and the process will repeat.

Is this efficient?

In a remodel early this year I did remove one of the radiator lines and one radiator. Should I have a pro come in?

Dale

Not yet

I guess I would confirm the pressure, I'm guessing you have the cut in set at 1/2 pound or whatever low you can set it, keeping the cut out to 2# or less. I would use an accurate gauge or the clear tube off the boiler drain trick "28 inches of water rise from normal off level equal to one psi" to check your installed gauge. I would make sure the end of the supply main heats quickly to your main vent. Are your rad vents opening quickly after the rad cools a bit? I think from your post that you are getting about 3 cycles per hour now, that is really pretty good for steam especially if you have removed a rad and probably insulated your house. If you want a real test open the windows for awhile and see if the boiler runs continuously as the rads are then condensing the max amount of steam. How's your water? If you drain a pan full from the bottom of the low water cut off does it boil like clean water in a saucepan? If you have an oil boiler you can reduce the input a bit, see what edr you have now and what the boiler is rated for. If you system is quiet and heats the house nicely most homeowners would trade with you.

matt_31

thanks for the info

The system is heating the house fine, the reason I'm writing is because there are now pauses in the boiler running instead of the continuous runs that it had done in the past. I was wondering if this is more efficient.

The system isn't all that quiet, I know why (16' section of level piping = about 7-8 bangs at the start of a heating cycle, there is no easy way to change the pitching so I have no plans to touch it )

I'm not sure how to accurately do the pressure test, I have already unknowingly done an idiot test and unscrewed one of the mains vents and got a pretty good blast of steam which was followed by the boiler turning back on. thank god no burns, but from the amount of steam that came out 2# is not out of the question.

The water in the boiler always has some rust in it. There was a card over the boiler which said every week to drain some water out of the boiler, so I do that and it is always rusty. I have tried to get the cap at the lowest place on the returns off so I can flush some water through but it won't budge and I'm not about to put enough pressure on it to risk breaking it.

gerry gill

Matt, its like driving

city driving is less efficient than highway driving..whatever can be done to get longer run cycles is more efficiant. has to be..the closer the gas or oil boiler can mimic the coal boiler, the better the system will be.

Unknown

Steam zen

Boy, Gerry, you think steam the same way that I do. Make it be like it was intended. I admire that in you.

Noel

steve_6

I agree with gerry

It sounds like your overfired. You should be firing to the connected load. Is this a new boiler or just a new vaporstat??

Mad Dog

How is your main venting?

Mad Dog

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Mad Dog

Yep - he good Noel

Hey M=Noel email me got a little somethin for ya. Mad Dog

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Wes_2

vaporstat: on, off, on, off

I have the same problem with my new, properly installed boiler EXCEPT the pattern is exactly the opposite. For the first 30 min. or so it does the on-off short cycle then for the next 30 min. it runs constantly without interuption. I've got a two-pipe steam system with the vaporstat set at 12 (main) and (subtractive) differential set at 4. Should I try the settings you suggested to Steve?

Thanks

Fred Harwood

on off

Wes, sounds as if your system has trouble clearing its throat, or getting steam through the mains and into the radiators. Once it does, condensing steam keeps the pressure down and relieves the fast cycling. Double check that your mains are venting fast and completely on start up.

Wes_2

vaporstat: on, off, on, off

Fred.

I've got two Gorton #2s on a tee at the end of my (well insulated) main which vent early in the short cycling period AND all new gorton valves on my radiators too. During the short cycling, the radiator vents breath in-and-out several times after each shutoff...any other ideas out there?
Thanks!

Fred Harwood

on off

Have you tried removing the mains vents, then observing the cycle? If the boiler shuts down on pressure at first, but not after the rads start condensing, something's in the way, IMHO. What size mains?

Ken_8

Steamhead, Noel and Mad Dog

We installed Steve's boiler a couple of weeks ago.

I am puzzled by the vaporstat setting being changed since we installed it. We left it at 16 ozs. off - 1 oz. back on.

This is NOT a true vapor steam system. I would prefer Steve return the vaporstat to the settings we left it, which would reduce short cycling substantially.

I also mentioned the cycle rate of the W/R stat (the cycle rate feature or setting) being an unknown - but I doubt it is a factor).

I suspect the fact that the boiler is 20% bigger than needed is another contributing factor.

This was done at Steve's request so we could place a steam radiator in the third floor - when that area is remodelled and converted from storage to heated living space.

Just in case we missed something, please continue the input. Ya never know, we may have missed something.



To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

Unknown

That's what I'd do too, Ken and Steve

And get the extra radiator on that system as soon as possible and run it.

Noel

Mad Dog

Hmmmmm???? In that case, Steve LEAve your cotton-pickin

hands off the vaporstaT...PUT IT BACK TO kEN'S SETTINGS..the man knows the Steam. I'm going through exactly the same situation with a customer and a recently installed boiler. I'm all for homeowners getting involved, but sometimes they need to back off and let us do our jobs.....some of them can micromanage and tinker too much. Mad Dog

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

nj_2

You can adjust the WR Thermostat

I had been having the similar cycling problems with one pipe steam system. The system runs great on 10 degree days but any warmer than that, the system cannot run 100% of the time, so there must be some cycling either by the pressure or the thermostat. The problem with the pressure is that it short cycles - 5 mins on 2 mins off, etc. and is very annoying and it seems to want to kill the boiler. The problem with the thermostat is that it would cycle 4 mins on 4 mins off, and that did not get steam to all the radiators. Then, I found out from this forum that the WR thermosat has an anticipator setting. I got ont he WR web site and found out that the anticipator setting is pre-set at 5 and can be set up to 40. After experimentation, I found that the setting 33 makes the system cyle well. 20 mins on approx 10 mins off--theres lots of time for steam to build up and almost never does the boiler kick off for high pressure. I'm not sure who on this forum told me about this--but this may work for you too. P.s. on my thermostat I think you press set time and set day at the same time and the ancitpator setting comes up,--but if you go onto their web site, you can get the manual for your model. mine was over 10 years old i believe