A Problem Child Steam System Input Please

Randy Berg_2

Steamhead, from a cold start thr system would run for around 3 to 5 mins, then off for less than 2 mins then back on for sometimes less than a min,then back off for less than a min. this would cycle this way until the stat cycled the system off on temp. It did heat the house very well. This was with a vaporstat, which I tried different cutin and out setpoints. Today I replaced the vaporstat with a pressuretrol and set the cutin at 8 ozs and cutout at 1 1/2 lbs. It did stop the short cycling, the on time was way longer also the off as well, it also heated the house very well, and no water hammer thru out the entire heat cycle, also no water problems at the boiler. I know that you are to crank the pressure down but this system seems to like the way I have it set now. Any thoughts to this? Now the system cycles like I feel it should.

Randy Berg_2

I posted last weekend about a system that was short cycling on the pressuretrol. Here is the complete system. The boiler is a W/M SGO3 which has a 356 sq ft rating. The header is 3 inch black pipe, there are two 1 1/2 mains, the longest one is 50 ft with a #2 Groton main vent, the risers are 1" which goes to Young Streamline copper convectors which does have air vents, the returns are 1" blk then reduced to 1/2" which drips into a 1" wet return in the basement. The other main is 30' with a #1 Groton main vent. After going thru Dan's EDR book this is the total sq ft of all the convector's 281 sq ft. All of the header and mains are insulated. The boiler has been cleaned and the returns have been flushed. The ph is 9.0. Also the near piping is with W/M specs. The system heats well and even but it does short cycle. There are not traps in this system. Also I notice last night that after the system cycles off thru the stat,about 1 min you can hear the #1 Gorton sucking air. On this main the total sq ft of convectors is 135.5. I hope that I have given enough info. In my caculation I am 75 sqft over, is this my problem or can I be over by this much, or am I overlooking something. Input please

Big Ed

Thermostat

Sometimes the wrong type of thermostat is installed . Some digitals are not made for steam because they have a "shorter " cycle used for warm air , electric heat or high volume hydronic systems . Steam need a long or no cycle thermostat . If you have a mecanical thermostat like a yo-yo ( the round type) or alike . They have a adjustible heat antisapater in which you can adjust to to a "longer "cycle.. I would look this direction for a problem assuming the mains and risers are insulated and you don't have any steam or condensation leaks..

Steamhead

That's actually a \"2-pipe, air-vent\" system

hard to believe they were still doing it that way when convectors came into use. But it WAS less expensive than Vapor, with the exception of the Orifice Vapor systems.

When you say "short-cycling", how long are the "off" and "on" periods?

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[Deleted User]

when it cycles off

are the convectors hot all the way across?

Randy Berg_2

On a call for heat the burner would cycle on and the convectors would not be hot all the way across before it would cycle on pressure, it would bounce off and on maybe 3 times before the covectors would be hot all the way across. When the system would cycle off thru the stat the convectors would be hot all the way across.

Unknown

you have not enough working vents, or not big enough vents.

That and a big boiler.

Noel