One pipe steam questions

steamsense

I have an oil-fired Weil-McLain P-SGO-3 one-pipe steam system in a roughly 100-year-old, two-story, single-family home. I don’t believe the exterior walls are insulated.

Originally, the system had 9 radiators. There are four upstairs and there were 5 downstairs across three rooms and a hallway. I removed two downstairs radiators: the hallway radiator and an extra radiator from one room. I left the pipes in case I wanted to put them back.

I improved the main venting by installing three Gorton No. 2 vents on the basement main. I also increased the venting on some of the slower upstairs radiators. The system now heats evenly and works well.

The thermostat is in the downstairs hallway near an exterior door, where I removed the radiator. Because that area stays colder, the rest of the house had been prone to overheating, although I got that reasonably well controlled last season.

This season, I want to explore individually controlling some radiators for finer room-by-room temperature control, using custom controls designed for one-pipe steam.

Broadly speaking, what happens to boiler operation when one or two radiators occasionally don’t accept steam for an entire heating cycle? For example, if the boiler fires 10 times per day and certain rooms are already warm enough to skip one or two of those cycles, does this create any meaningful operating problems?

The system was originally designed with 9 radiators, now has eight permanently connected, and could sometimes have only six or seven accepting steam. Would that cause pressure to rise more quickly, increase short-cycling, affect system balance, or create any other issues?

My boiler never gets above 2 PSI. I removed the old pressure gauge and installed a digital pressure sensor so I can monitor it more accurately. Two PSI may already be higher than necessary. Would lowering the pressuretrol setting make individually controlling the radiators work better, or would it simply cause the boiler to cycle on pressure sooner?

I’m a plumber by trade, but my steam experience is limited because it isn’t something I work on every day.

Thanks

leonz

Please purchase these three excellent books about steam heating from the Heating Help Bookstore Page before you proceed further on your homes heating system.

1. STEAM HEAT REVISTED
2. GREENING STEAM
3. WE GOT STEAM HEAT

If it were me I would put that radiator back in place and just turn the vents upside down to prevent them from expelling air and only flip the vents up when needed.

You could use very expensive trvs but flipping the vents upside down is simpler. adding too many trv's only complicates things where changing vent sizes on the radiators is simpler from what i remember reading.

The three books Mr. Holohan wrote on steam heating mentioned above will help you balance your system.

Hap_Hazzard

One way to reduce the output of a radiator is to put it in a poorly designed cabinet Lots of people have discovered this the hard way. The more you can restrict airflow through the radiator and block radiant heat, the sooner the radiator will stop condensing water and liberating heat. For your purposes, a cabinet with adjustable louvers might do the trick, but it will take some trial and error as well as decent carpentry skills.

ethicalpaul

I would consider moving the thermostat to a more representative living area before I started messing with individual controls on the radiators (although lots of people have and like them)

When a radiator misses some cycles it will effectively oversize your boiler (more) but that's probably not much of a concern since as you say, your pressure isn't going above 2psi

You don't really need to mess with your pressure control if you are never going over 2psi either, unless you'd like to keep it even lower. I have mine on a low pressure switch and timer system where if it sees like 10 inches of water column (about 1/3 psi), it will interrupt the call for heat for 10 minutes.

All our boilers will operate fine on MUCH lower pressures than 2psi of course, and they often are doing so. Only on days with long heating cycles should you see the pressure rise at all anyway, if your boiler is anywhere close to correctly sized.

Jamie Hall

As said above. First, move the thermostat to a more reasonable location. Amazing what a difference that can make. Second, balance the system by varying venting rates as much as you can to the way you normally like it.

Then you can think about thermostatically controlled vents to shut off certain radiators. However, keep in mind that they can only stop (or nearly so) a radiator from heating at the beginning of a boiler cycle. Once a radiator has started to heat, closing the vent will do very little — so the boiler must cycle for them to do anything. Also keep in mind that they won't turn the boiler on!