Short Cycling One Pipe Heating System

Carl M.

Hi.

My steam heat wasn't heating the house at all and cycling a lot; so I recently replaced my main vents with 1/8" Jacobus vents and started getting much better heat and started using a lot less oil.

However the system is still cycling (although for a much shorter period of time). All of my radiators are hot so I don't think that I have a problem with the radiator vents; and I also think that I have enough water in the system.

I'm also having a problem with water hammer but can't quite figure out where its coming from. How do I find it?

TIA
- Carl M.

Pete_18

short cycling

Hi Carl,

When it's cycling off, is the thermostat up to temperature? Basically what I'm trying to get at is whether the thermostat or pressuretrol is kicking the system off.

What type of thermostat do you have? Have you checked the anticipator setting on it (or heat dipswtich setting if they have a newer digital thermostat?)

On my system, the thermostat which was an old T87 with a non-functional/misconfigured anticipator was constantly short cycling (ran 3-4 mins at a time every 10-15m).

When I replaced the thermostat and went to the steam setting on the new T87 digital, it appeared to be long cycling and idle too long (1.5-2.5 hrs between cycles), and now I have it set at the hot water setting / 3 cycles per hour it appears to run less time but a little more frequently, so that the boiler isn't cold starting each time it fired up.

Pete_18

water hammer

Mine was happening right next to the boiler where steam was running in to condensation on the return. It could also come from your radiators and mains/radiator runs if they're not run/pitched correctly.

Maybe someone will have better advice but I really just needed to keep looking around and listening until I could figure out where my water hammer was coming from.

Carl M.

I have a RiteTemp 8035C and its definitely *not* up to temperature when the system is cycling.

The thermostat has a jumper in the back that allows the installer to set it for gas or electric heat; in the "gas" mode it uses an anticipator but in the "electric" mode it does not. I set mine to electric the last time I played with it because I'd heard of this problem.

However, I didn't know what a "pressuretrol" is when I read your reply; but I found a good article by Mr. Dan himself here:
http://www.masterplumbers.com/plumbviews/2002/BasicSteam.asp

Armed with more information (i.e. knowledge of the proper function of the pressuretrol) I think that my system is generating "wet steam" and short cycling. If I start it cold at 60F, it takes about 40 minutes to generate steam (the boiler & burners areancient) but it takes about 2.5 hours to get the house to 70+. I changed the vents on my radiators and on my mains recently so I don't think that they are the problem.

Once the radiators get hot the system cycles on and off; (on for 20+ minutes, off for 10, etc.) but as soon as the system cycles off I hear a lot of condensation and gurgling. Once the system's back on I get air venting out of all of my vents and water hammer on the side of the house farthest from the boiler. I think that my mains, feeders, and radiators are properly pitched though.

Is this symptomatic of "wet steam"? If so how do I fix that? Is a new pressuretrol in order?