Short cycling indirect oil steam system

Daniel_3

By indirect I mean the water heater is hooked into the Burnham boiler. I could be wrong on the terminology though. This is my sister's house which I am trying to help her out with. All the service on this boiler was done by guys who know very little if anything about one pipe steam. Her boiler cycles quite often and there are some issues that need addressing namely 1.) insulating the pipes, 2.) replacing a riser in 1 inch copper (*puts hand over face and hangs head low*), 3.) installing main vents, 4.) re-piping the header which utilizes only one supply when there are two tappings. The boiler services 396 sqft steam and I don't remember how many sections. I'll have to calculate the steam in the house to make sure it's sized right. There are 11 rads in all of normal size. All 38" A&R co peerless from two to 9 sections and some are 32" in the same configuration.



The one thing I'm not sure of is the need for short cycling in an indirect set-up. Of course the water is not being used for the heater to call to temp when the short cycling occurs so my guess is the above issues will probably solve the short cycling. How can the water heater affect the firing time?

Jamie Hall

Really need more information...

Particularly the boiler size and its rating at whatever its being fired at (note that you need to know the firing rate, as well as the nominal boiler size to know what it's putting out!) and then the total EDR for the radiators -- there are helpful links on this site for that, which I don't recall at the moment.  Also what do have in the way of vents?  On the radiators?  On the mains?



The near boiler piping doesn't sound optimum, but that won't cause short cycling (unless it's really truly horrid).



Nor should using the boiler for hot water -- there is an aquastat on the boiler for that; if the boiler is also being used for heat, that should do it.



What can cause true short cycling -- if that is really what you have -- is either a boiler which is significantly oversized for the load it is serving (see above) or seriously deficient venting.  In the first case, the boiler is producing more steam than the system can use, the pressure rises, and the boiler cycles.  In the second case, the air can't get out fast enough, the pressure rises, and the boiler cycles.  Can't tell which you have without the additional information!



Another possible cause, which isn't really short cycling, is a thermostat which isn't set up right.  The older thermostats had anticipators; newer ones have a "cycles per hour" adjustment -- or should.  For steam, that should be set at one cycle per hour.



Insulating mains is always a good idea!  Won't do anything about the short cycling, but sure can save serious green...

Steamhead

396 square feet...............

is that a MegaSteam boiler?

nicholas bonham-carter

short-cycling sister

if her main vents-[not radiator vents] are not up to the job, then her fuel company is being paid extra to squeeeeeeze the air out, often causing short-cycling, not to mention excess fuel consumption. this is especially true if her pressure is too high. they say that high pressure kills-in people, but in steam, it just impoverishes the owner!

check the main vents first, and even if working, are probably not capacious enough.--nbc

Daniel_3

V8

No main vents at all as the first post reveals. A variety of Ventrite no.1's and Heattimer vari-valves for the tough to heat radiators. This will change of course once the source to the destination is fully balanced (boiler to radiators) I would not say this boiler is over-sized at all but maybe a tad under. I'll have to calculate the radiator edr values. The boiler is a Burnham V8  with a model number of PV84 something or other. Again the steam square foot is 396.  Maybe 5-10 years old? I'd like to get a picture of the supply and header but simply put it uses only one full sized supply at 2" and into a 2 1/2" header where the two main are served. It's not too bad actually. There is no bull-heading and an equalizer does exist with a hartford loop. The pressuretrol was set at a main of 2 and a diff of 1.5. Aquastat toa Burnham hotwater heater which as stated is not calling since the water is not running. I sense all the above issues plus a boiler that's slightly undersized may cause the pressure to cut off boiler.