Upstairs radiators are very oversized

Waterbury Steam

I've been working on my two pipe steam system for the past several years and I've gotten to the point where the system is nicely balanced most of the time. When outside temperatures are above about 20 degrees, the system heats nicely and evenly without building any more than about 2 oz/sq in of pressure. None of the radiators get filled enough for any of their steam traps to close at these temperatures. All of the radiators get hot within a couple of minutes of each other and I don't see any temperature differences between rooms greater than about a degree. It's very comfortable.

This all goes out the window when a cold snap arrives. Calls for heat get longer and the upstairs bedrooms can climb up to about 78+ degrees while every room downstairs maintains the 71 degrees that I set on the thermostat. I did heat loss calculations for every room and compared them with EDR of currently installed radiators, and made adjustments for radiator boxes where they exist. What I found is that all of the downstairs radiators are properly sized, while each bedroom has a grossly oversized radiator. According to my estimates, I should have about 12-13 EDR for the guest room and the nursery, and about 25 EDR total for the master bedroom. As it is now, the nursery and guest room each have a big 30.25 EDR rad, and the master bedroom has two of these monsters for a total of 60.5.

What I think is happening is that when colder weather creates long heat calls, the downstairs radiators reach capacity and the traps close, redirecting all of the steam upstairs to the oversized rads which still have open traps.

I tried installing Danfoss TRVs on these four rads a couple of years ago and did not care for them. I changed the valves back to Hammonds this year. The TRVs worked during cold snaps, but during more typical 20 degree + temps, they left the rooms cold. These valves do not open nearly as far as a standard radiator valve and I think they restricted the steam flow enough that it just went to fill other radiators. The TRVs were installed properly, sticking out sideways away from the radiator.

Right now I'm managing this by throwing an MDF slab on top of the radiators and draping a light blanket over them. It's comfortable up there now, but as soon as the cold snap is over I'm going to have to take the slabs and blankets off. I'd like a way to solve this so I don't have to mess with these radiators throughout the heating season.

Some ideas I had:
1. Put the TRVs back on, and throttle every other radiator with a standard valve to try to match the flow restriction of the TRVs. Seems like it might be hard to do effectively.
2. Build radiator boxes upstairs. This would help, but probably won't give me the 50% reduction I'm looking for.
3. Buy some correctly sized radiators and replace the oversized ones. Would probably work best, but would be expensive and labor-intensive.
4. Switch from 1 cycle per hour to 2 cycles per hour to shorten heat calls. Not sure if this would work, but seems worth a try.

Any advice on the best way to handle this problem?

Jamie Hall

Shortening the cycle from 1 to 2 may well work wonders in your situation.

Fred

Is the main that supplies the second floor a different one than the main that feeds the first floor? If it is, can you slow the venting down on that main that feeds the second floor enough to get a better balance or increase the venting on the first floor main to achieve a better balance?

Waterbury Steam

The same mains feed both upstairs and downstairs rads.

SteamCoffee

One word...orifices...

MilanD

Since it's 2 piper, just throttle down the upstairs rads if they are too hot.

Waterbury Steam

If I do orifices or throttling down, won’t I end up with the same situation I was in with the TRVs? It’ll work fine on really cold days but won’t heat the rooms very well when it’s above 20 degrees outside.

MilanD

On warmer days, open it back up...

Fred

I wouldn't recommend down sizing the radiators. That will only contribute to over-sizing the boiler and just change your problem from one of over heating to possible short cycling. It may be that you or the occupants of those bedrooms may have to throttle the rads down to their specific comfort level. Maybe if you can mark the valve for a "Normal" day and another mark for "Cold" day once they have found their comfort zone.
I would think though, if an orifice was drilled for a cold day, which would be the max amount of steam it allows into the rad, the boiler cycle time would be shorter and take care of the warmer days.
One other thought, where is your thermostat? If it is in the coldest or most drafty room in the house or on an outside wall, or has a hole in the wall behind it that allows a draft to blow up behind it, that it may cause the boiler to run longer than it otherwise would if it were in a more moderate room or on an inside wall or had insulation pushed into the hole.

Waterbury Steam

I’m going to try 2 CPH and see what happens. If that doesn’t work I will probably have to manage with manual throttling.

nicholas bonham-carter

Or moving the thermostat upstairs.—NBC

PMJ

I used to have exactly this problem with my two pipe. Way more heat upstairs in the bitter cold and cooler than downstairs in moderate weather.

Increased cycles definitely helped - I use 3 cph. The suggestion to simply have two valve settings upstairs is a good one and not that much trouble. But I kept looking for solutions that didn't require even that.

The most amazing improvement though came from vacuum. When you cycle and let your two pipe system sit most of the time in vacuum most of the steam goes to the rads in the coldest areas like magic. So as soon as the upstairs got any warmer than the downstairs vacuum saw to it that downstairs rads got more of the total than upstairs rads.

What I have learned is that when a system is in vacuum where the steam goes is determined by which rads are condensing steam the fastest and not by valves and vents. Steam is condensing the fastest in rads in the coldest areas so it is all self adjusting. Not perfect - but way better than pressure based distribution.

I will also point out that I think it may be missed how high a percentage of the time I am actually in vacuum naturally without pumps. In bitter cold firings are 7-8 minutes 20 minutes apart +/-. My boiler is so oversized I have never seen even a 50% net burn time required to heat at -20F. The first 4-5 minutes of each burn is still in vacuum + all the burner off time so I am only NOT in vacuum 12 minutes or so an hour.

Two pipers should really try this. How different it is will shock you.

Paul48

@PMJ

If his upstairs radiators are greatly over-sized, how will getting more steam to them benefit him? Based on your description, the larger radiators will always condense more, and therefore get more steam.

PMJ

Paul48 said:

@PMJ

If his upstairs radiators are greatly over-sized, how will getting more steam to them benefit him? Based on your description, the larger radiators will always condense more, and therefore get more steam.

@Paul48 ,

I didn't mean to say physically bigger always condenses more.

What the steam does with the system in vacuum is completely different than when you push it with pressure. I am a mechanical engineer and I have been fiddling with this thing for nearly 25 years and I'm still observing and learning new things. If someone had told me about this prior to my own experience with it I probably would have said no way.

First of all, when you run shorter cycles right out of the gate you don't fill any rads so they are more the same "size" to begin with. Running straight to tstat satisfy like most people do you fill things more than needed so things get more out of balance right away. In this case where the bedroom rads may be oversize harking back to the "night air open window" days. Mine are too and I just don't fill them - ever. But that aside, the rate at which a radiator will condense steam (full or not) seems much more related to temperature of the air around it and the temperature of the objects in the room it is radiating to than its physical size. But when it occurred to me that the original design for the operation would never fill them up, I began trying to run that way. When I did, radiators became more similar in size, and then big ones in the colder rooms just kept taking a higher percentage of the total every cycle while in vacuum and kept filling up as needed to even the temperature out - all on their own. I admit that as I observed this I was startled at first.

I think the best example I can give is let's say I have two identical radiators, one inside a room at 70 degrees and one in the garage at 45. On startup we fill them both pretty close to the same amount with pressure. But the way I run that is where the similarity ends. The one in the garage is obviously condensing a lot faster than the one inside. Because of this the vacuum created there is slightly deeper than in the other one. When I shut down after a short burn in a closed system, the garage rad continues to pull steam from the main - considerably more than the other one does. When I fire again say 15 minutes later, for about 5 minutes the system will still be in vacuum, new steam goes there faster and condenses faster again. When you consider that the system is in vacuum like 80% of the time, the garage rad, though it is exactly the same size as the one inside, will condense considerably more total steam than the inside one. This is because with the system in vacuum most of the time the lowest pressure in the system is in that rad. Lower by a small fraction of an ounce, but that is all it takes to determine what happens with the steam. It would also condense more in a pressure operation too, just not nearly as much more since when the burner goes off vented, air goes in and flow of steam from the main stops instantly. There is minimal if any balancing going on the entire time the burner is off in a vented system. I will point out here that with a coal fired vapor system running at single digit ounces at the header, it is very likely that there was actually slight vacuum in rads in colder locations all the time doing exactly what I am talking about here continuously.

Now temperature differences inside the house are much smaller but the principle is the same. Tiny differences in vacuum pulling steam means a little bit more steam goes to the colder places each and every cycle, and it really adds up. Not only that, but wind and sun changes where the coldest places are. Vents and valves don't adjust for these things. Vacuum does - automatically.

Bottom line, try to picture partially filled radiators initially filled about the same. Then try to picture the ones in the colder rooms - even just by fractions of degrees - drawing a bigger share of the steam than those in the warmer rooms a little each and every cycle. The net balancing effect is quite significant.

Paul48

Fact is fact......but you have to admit......it seems counter-intuitive, doesn't it?

Waterbury Steam

PMJ, was your system initially a vacuum system or did you convert it? I’m wary of trying vacuum with my estimated 20 year old boiler.

PMJ

Waterbury Steam said:

PMJ, was your system initially a vacuum system or did you convert it? I’m wary of trying vacuum with my estimated 20 year old boiler.

I converted it - though that didn't take much. Originally Mouat vapor with vented dry return though what I moved into had the main vented too( and a number of rads).

Are you worried about damage? My boiler is 61. I am seeing now 60-70 inches water vacuum on every cycle which is plenty enough to do wonders with balancing. That is what - 2-2.5 psi. I don't think that is enough to worry about if that is your concern.

PMJ

Paul48 said:

Fact is fact......but you have to admit......it seems counter-intuitive, doesn't it?

Yes it is. Truly, I had to see it for myself. I probably would have been a tough sell. But in two pipe it was so easy I said why not try?

It doesn't take much reading to see that the dead men were very interested in vacuum. There are good reasons for that.

mikeg2015

Stack effect! Cold air infiltration downstairs, exfiltration upstairs. Plus heat rises up the stairwells.

I have the same issue. Actually upstairs is too cool over 35f. Perfect 20-35, under 20 downstairs is colder.

I have 1 pipe so I can tweak ventrite adjustable vents then balance it with my heat pumps after that. Heat pumps take over the load above 40-45.

Canucker

@PMJ I wonder how big a difference a vacuum system is compared to one set up like @ChrisJ where he runs less than 1" w.c. most of the time? I would think running in a vacuum would give you a larger cushion to work with when balancing the rads. Like you say, if it's two pipe why not try it, it could be quicker to balance everything compared to the conventional way.

ChrisJ

I'm not sure how good or bad the Ventrites are yet, I have a few on my new TRV's I'm trying out.

If you're having issues getting steam to a radiator fast enough using a wide open Hoffman 1A, try a Gorton #6 or even a Gorton C. Just be careful not to go so far as to cause the steam to skip across the bottom of the radiator and shut the vent fast.

I'm not sure on vacuum systems as I've never worked with one, but I suspect they are easier to deal with. The pressure on the boiler side is moot, what matters is the pressure difference between the boiler and the end of each radiator.

For example, Titanic's center turbine had an input of 9 PSIA, about 10" of mercury vacuum (vacuum) and the output was 1 PSIA or 27.89" of mercury and it produced 16,000 HP even though it's input was a vacuum.

With a vacuum system, atmospheric pressure becomes meaningless, also known as "PSIG" or what most of us commonly use to measure tire pressure, boiler pressure etc. All that matters is the pressure difference between point A and point B.

PMJ

Canucker said:

@PMJ I wonder how big a difference a vacuum system is compared to one set up like @ChrisJ where he runs less than 1" w.c. most of the time? I would think running in a vacuum would give you a larger cushion to work with when balancing the rads. Like you say, if it's two pipe why not try it, it could be quicker to balance everything compared to the conventional way.

Let me preface my response by saying I really don't want to be in the position of suggesting anyone's system is deficient in any way. What I do can only really be of interest to a very small group anyway. Contractors are simply not going to be able to get paid to work with this except in very unusual cases.

Really well run conventional vented systems like @chrisj has are great. Remember, he also has the Ecosteam control which spreads out the burns well beyond what a conventional control would which is a big deal in keeping the pressure low. With a header pressure as low as his I do think his rads would be bordering on vacuum themselves and doing some natural balancing - while the burner is running. But what about all the rest of the time? It is all the rest of the time (which is most of the time) that people don't consider much.

I would just ask that you consider what is going on all the time the burner is off in a vacuum vs a vented system. The second the burner goes off in a vented system things run backwards from what you want. Air begins entering the rads immediately chasing steam back to the boiler (the giant sucking sound from a recent post). Zero balancing of more steam to colder areas is going on in all that time. The biggest thing I noticed after I started introducing vacuum was how much longer the feed pipes to all the rads stayed too hot to touch after the burner went off because steam was still going into them rather than room air being there. Some boiling is still occuring in my boiler 4-5 minutes after the burner goes off due to the drop in boiling point. My system is still sending some steam to all the rads during the entire burner off periods. This is a lot of time! Boiling starts sooner and steam travels faster on every new firing. This all does add up to something.

@Canucker, it is difficult I think to really appreciate how much really positive activity goes on between firings in a vacuum system without experiencing it. It is a lot of time which adds up to a lot of activity. I admit it has surprised me. I can tell you it ends up being much more even heat and incredibly quiet. This discovery has made steam heat much more enjoyable at my house. So to me it is a really big difference. I hope I can say that without anyone being offended. I truly wish there was an easy way for more people to try it.

zoom

PMJ - what are you using on your venting to allow for air elimination and then sealing to create a vacuum? I could not identify many good commercially available options?

PMJ

> @zoom said:
> PMJ - what are you using on your venting to allow for air elimination and then sealing to create a vacuum? I could not identify many good commercially available options?

One 1/2 inch 24vac solenoid valve on the dry return. System is 1000EDR. It is 10F out today and it is open only 6-7 minutes total each hour. Shockingly little venting is required when you don't let the air back in.

There is a simpler way to get going though. There are cheap plastic check valves with pretty low cracking pressures you could start with so no actual control is required. I have one plumbed in as a safety release should the solenoid fail. I went to the solenoid to get below the cracking pressure.

Canucker

I believe you @PMJ , I boil different solvents at different pressures all the time with different temps to the glass condensers. I've seen exactly what you're talking about and can definitely picture it in a steam system.

Waterbury Steam

So let's say I currently have a 2-pipe system with dry returns and a condensate pump. To try this system with the check valves, would I just put a check valve on the condensate pump vent? Would this affect the operation of the pump?

PMJ

Waterbury Steam said:

So let's say I currently have a 2-pipe system with dry returns and a condensate pump. To try this system with the check valves, would I just put a check valve on the condensate pump vent? Would this affect the operation of the pump?

In 2 pipe when you check valve off the returning air the entire system(supply and return) sinks into light vacuum. But the relative pressures between everything in the system to each other remains the same less the minute changes in the rads themselves I have discussed elsewhere. Gravity is still gravity. I don't have hands on experience with vacuum and a condensate pump but I'm willing to bet there would be no difference in that either. Everything is the same relative pressure to each other just as it was. You have just shifted the average pressure over a little.

This is a residential system?

Waterbury Steam

Yes, residential. About 430 edr total. The condensate pump doesn't really need to be in the system--if this boiler is ever replaced I plan on converting it back to gravity.

PMJ

Waterbury Steam said:

Yes, residential. About 430 edr total. The condensate pump doesn't really need to be in the system--if this boiler is ever replaced I plan on converting it back to gravity.

@Waterbury Steam , You are good to go then. Remove all vents and put one of these:

https://www.mcmaster.com/#45275k42/=1azdw2o

somewhere on the dry return or maybe on your pump vent - that's it, done, no additional control and you are a vacuum system. What's to lose? Problems? Put the vents back on like you were.

Ok, go ahead and have a good laugh everyone. I still have one of these on my system as a safety backup. It has a cracking pressure of about 8 oz so with my solenoid I never go that high and it never opens. If the solenoid failed to open the system would run with this check same as it did with this for several years. Works fine, and at that price no excuse not to try. When I was first starting out on this I looked for a no cost no risk thing to try. No temperature to speak of on the dry return (or shouldn't be) so why not this I thought. Worked great.

I keep saying it but it seems there are few believers - warming up a system from room temp the first time takes way longer than to vent all the air through a very small opening. After it is warm, if you don't let the air back in, on all subsequent cycles there is only a tiny fraction of the venting required that everyone is used to so one small vent hole is plenty for that too. Nothing beyond this one check is needed. Done it for years. Not a theory.

Waterbury Steam

It's worth a shot. I've got a few adjustments to my venting to make before I can try it but it seems cheap and easy enough to do.

nicatniter

I use one of these at the end of my dry return after removing the spring to reduce cracking pressure. The system stays in vacuum between cycles and pushes steam at 1-2 ounces after that.

PMJ

nicatniter said:

I use one of these at the end of my dry return after removing the spring to reduce cracking pressure. The system stays in vacuum between cycles and pushes steam at 1-2 ounces after that.

Great! Many different ways to do this. Nothing critical about it. Anyone with a two pipe system please consider putting an end to running your system as an air processing machine.

nicatniter

I agree! I'll note that my system isn't totally airtight, as the vacuum will gradually dissipate over longer periods of time (say an hour) -- but with ~25 minutes between cycles it stays well below what my gauge will measure on the negative side (it pins at about -32 ounces). One of these days I'll see if I can tighten it up, but I know one flaw is a pinhole leak in a convector that used to spit a little steam back in the dark days when I was running at higher pressure. That will be tough to fix I suspect.

PMJ

nicatniter said:

I agree! I'll note that my system isn't totally airtight, as the vacuum will gradually dissipate over longer periods of time (say an hour) -- but with ~25 minutes between cycles it stays well below what my gauge will measure on the negative side (it pins at about -32 ounces). One of these days I'll see if I can tighten it up, but I know one flaw is a pinhole leak in a convector that used to spit a little steam back in the dark days when I was running at higher pressure. That will be tough to fix I suspect.

Exactly! you don't need a really tight system to take advantage vacuum as you have found out. I keep saying this but I think many are afraid to try because they think super tight systems and pumps are required. Not so at all. First cycle means nothing when you really need heat because there aren't any of those! After that 2-3 cycles per hour and you are in vacuum 3/4 of the time - even with a leaky system. Venting concerns disappear altogether.

neilc

nicatniter said:

I know one flaw is a pinhole leak in a convector that used to spit a little steam back in the dark days when I was running at higher pressure. That will be tough to fix I suspect.

How low a pressure do you get up to?
I would think JB or 2 part might seal it up if you can get to it

nicatniter

Sorry to hijack your thread @Waterbury Steam ...
@neilc I'd need a better gauge to tell for sure, but at least -32 inches H20; I have seen charts on this site going to -40
I may try JB weld but at this point - good enough!

neilc

I meant plus side pressure,
that's what would blow the patch off,
or temperatures , , ,

nicatniter

It operates at between 1 and 2 inches H2O during steam cycle. Hardly breaking a sweat. Vaporstat is set on 5 with 4 differential. It never shuts off on pressure during normal operation, but then I do keep the thermostat constant 24-7.

Waterbury Steam

> @nicatniter said:
> Sorry to hijack your thread @Waterbury Steam ...

That’s perfectly OK. When you took the spring out of your check valve, did you orient it facing upwards so gravity pulls it closed?

nicatniter

Yes - an arrow shows flow direction, so that end should be facing the atmosphere, and the bubble valve is held in place by gravity. Here is a photo.
Note that I don't have a vent or anything downstream of this... didn't really see any reason to, since I have crossover traps to keep any steam out of the dry return. But maybe that's too optimistic, so a Gorton tree would probably be good to add.

nicholas bonham-carter

Can the hole be plugged with a small screw in the (tapped) hole?
—NBC