Why such low run times on steam boiler?

Mike Cascio

Hi,

For us here in New Jersey, we have been having quite a good cold spell (15-25degree days) and this has allowed me to monitor how our one pipe steam system is operating. Even on a day where it is below 20 degrees outside, the boiler only runs a cycle of six minutes. The heat anticipator on the T8090 thermostat is set to 1.2 amperes. When the boiler was installed 12 years ago, the installers put a T87 thermostat in and had the heat anticipator set to .8 amperes. The gas draw is .8, but the run time was only 5 minutes or less. I moved it to 1.2 amperes and it gained around a minute or so run time. Why with the heat anticipator set so high is the boiler running such short cycles? I dont think the thermostat is defective because the previous T87 did the same thing.I also know it is not a pressure related issue, the boiler is set to cut in at .5 lbs and cut out at 1.5lbs and it takes a good half an hour to build up any pressure. The radiators in the room of the thermostat are throttled back with the vents to compensate for the deficencies in the rest of the system. These problems are to be fixed after the heating season is over. The room where the thermostat is, is also over the boiler room? I know that the boiler's optimum run time is at least 10 to 20 minutes, why is this boiler running so little?

Any help would be greatly appreciated.
Michael J. Cascio

Luis_2

Shortcycle

Hi.Finally someone have same problems.I'm in E.Orange NJ.On Dec 16th posted same situation, and still not really solved.I did beleive that having the thermostat over the boiler could produce the situation where the T87 gets satisfied be4 the boiler have a chance to heat all 3 floors.What I did was to change all the rad-valves in the first floor to Vapormyst #6 .I did replace my 3rd floor D and C valves to the 2nd floor.Placed new C and 2 Ds on the 3rd floor.It seems to had balanced the heating( at least all radiators are hot 1/3rd of the way) of the house.Moved the pressuretrol cut in to 1.0 and the cut-off to 1.5.
I'm not a plumber, so don't take my experience as advise. My boiler still clicking every 10 min. working for 3or4 min all day.The thermostat is set at 7o* and the room(DR)temp is @72*.Please help.

thfurnitureguy_4

Is your house warm and evenly heated?

Boilerpro_3

Check this

If the boiler is directly under the stat, and the boiler area is usually pretty warm, that warm air can make it up the hole for the thermostat wire and cause it to be satisfied too quickly. You may just need to plug the hole in the ceiling.

Boilerpro

Steamhead (in transit)

Mike & Luis, those boilers

may be oversized or overfired. It's time to call in a pro to evaluate this. Try the Find a Professional page of this site.

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

Dale

Off switch?

IMHO, What you need to determine FIRST is what is ending the run cycle. What switch is opening? There are several in series in a typical steam system, the stat, the Low water cut off(s)and the pressuretrol,spill or rollout on a new system all are just switches. So, is the house at the temp you set when the burner cycles off? If so then the stat is the switch that's probably opening and your boiler is too big for your rads at that given outside temp. If not, if the house is cold and the boiler cycles off jumper out the stat and see what happens, if the boiler runs longer than the stat is bad. If the boiler runs a short time with a jumpered stat then one of the other switches is opening, if there's plenty of water in the gauge glass and it's stable then my best guess is the burner is stopping because the switch in the pressure trol is opening. A pro can put a meter or test light on the switch contact screws to confirm this. If true then why? If set correctly 1/2 or less on when running and max 2#OFF, Perhaps the pigtail feeding steam to the pressuretrol is clogged but, The usual answer is the steam isn't getting out of the boiler to the rads as fast as it's produced. The IMHO most common reason for this is dirty boiler water. VERY few installers skim enough if at all. It could be perfectly good boiler water ( still stinky ) but not enough main vents or rad vents or poorly pitched pipe or a partially clogged pigtail or poorly insulated pipe, or a greatly oversized boiler, or alot of other things. If you have a big setback and the pipes get real cold a good system can condense so much on startup that it will need a warm up cycle to be normal. But, first find out what switch is shutting off the burner early.

Mike Cascio

The boiler is shutting off on temperature, not pressure, low water, or any of the other switches that break the circuit. It also does not seem like the boiler is oversized by any great degree, the steam moves at a slow velocity.

Still dont get why the boiler runs on so many spurts rather than a long steady burn.

Thank you for any help,
Michael J. Cascio

Mike Cascio