Throttle my steam system on warmer and colder days?

speedbird

Hi everyone, thanks to a lot of you, my system is running great. It's quiet and well balanced across rooms and floors. I have a 3 story house, I keep the thermostat at 69 all season, with the upper floors at 65, through venting/sizing (average temperature day).

What I've noticed, is on colder days the upstairs will get much much hotter, given the load on the system is higher. On warmer days I have to shut off vents on the first floor to increase load enough to get the steam upstairs. I was thinking of putting a danfoss thermostatic valve on the large radiator next to the thermostat (with a large vent), to act as sort of a throttle. On warmer days, I'd turn it I'd lower or have it off, on colder days I'd crank it up, with the effect of changing the load on the system.

Am I thinking about this the right way? Are there other things I could be doing that could achieve this? Again, everything runs really well, so don't want to mess around too much. Thanks again.

Jamie Hall

Before you go to the trouble of a thermostatic vent (since I gather you have one pipe steam -- you don't want a thermostatic valve on the inlet!) make sure that your main venting is adequate. If it really is, then -- unless you want your upstairs cooler -- make sure that the radiator venting is really properly balanced, so that all the radiators start to get steam at more or less the same time (the farther ones will be slower, but shouldn't be more than two or three minutes slower, even in a large house). This may probably will mean putting smaller vents on radiators which are heating too fast.

Then, and only then, if the system is still poorly balanced, you could try a thermostatic vent...

speedbird

Yes, sorry a one pipe system. There are 4 Gorton Size 1 vents in the basement. How do I tell that that's enough? Everyone who looks at my boiler always comments on how well it was piped/installed, so have to assume some level of expertise went into the 4 vents down there?

We do like it cooler upstairs, and on regular days it is perfectly cool upstairs, at 65. But when the temperature really drops it gets much much warmer up there, or if it's warmer outside it gets too cool up there. I have pretty small vents on the 1st floor, especially near the thermostat. Again on most days everything is perfect.

Maybe I could use 1 or 2 Gorton Size 1 vents on the 2 mains/risers further away from the boiler, so your point about getting steam to all the radiators at the same time?

Jamie Hall

How big -- diameter and length -- are your mains? It is possible that if they are relatively short and small that the four Gorton #1s are enough. It's also unlikely. A Gorton #2 has 3 times the capacity of a #1, and sort of a base rule of thumb is 1 Gorton #2 for each 20 feet of 2 inch pipe... Also, any main vents should be as close to the end of the mains as possible (though not right at the ends).

PMJ

@speedbird , you are certainly on the right road with your thinking, though any remedies will be elusive, especially in one-pipe.

This is a great example of how conditions change constantly and they all simply can't be handled by one setting of vents and valves. Pressure driven steam is distributed the same way every time unless someone changes the vents and valves. The trouble then is that which rads you need to heat and which ones you don't to keep things even is constantly changing due to wind, sun, and yes outside temperature. That room with the warm afternoon sun needs next to nothing some days while at the very same time the one on the opposite side in the shade and sometimes wind on top needs a lot. No one setting of vents and valves can possibly handle this change, just won't happen.

I too had the upstairs/downstairs syndrome just as you describe it when my system was open vented. Drafts up and down within a house increase the colder it gets outside - they just do. But I have a 2-pipe system. And what I found is that if your system spends most of its time in vacuum the flow of the steam is entirely different. In vacuum more steam (a lot more) flows to the rads condensing steam the fastest, and those obviously are the ones in the colder areas. Sometimes that is upstairs, sometimes that is downstairs. Sometimes north side, sometimes south side. There is a tremendous balancing effect with the vacuum and it is completely self adjusting to the conditions. My upstairs/downstairs disparity has vanished entirely, as well as many other like issues and I never touch any valves. I assume many are thinking this is too good to be true. To that I say it must be experienced first hand. Dramatically different is the way I would put it.

Fred

How long is each main and what diameter pipe? If one main is significantly longer that the other or larger diameter, there will be more air to push out of it which means there should be larger or more vents on that main so as to move the air out at about the same time as the smaller main. Having the same amount of venting on each of two mains, when those mains are not of equal size means that steam will start to push into the radiators on the smaller main than it will in the radiators on the larger main.

speedbird

Thanks all, very helpful responses. I’ll do some measurements this weekend. I do know that I had to buy about 250 feet of insulation to wrap all the pipes down there. Obviously not all of that was mains. It’s a good size basement, about 1500sf, with 4500sf upstairs, across about 18-19 radiators.

The 4 Gorton 1 vents are definitely all at different distances from the boiler, but also slightly different diameter piping. So I’ll have to look a little closer this weekend.

New England SteamWorks

You need much bigger main vents. After that, you need to balance the system with the individual radiator vents.