Sizing steam down to correct heat loss instead of up to oversized radiation

ethicalpaul

In this thread, @Jamie Hall said:

if you are looking at a steam system installed in a house which has had significant envelope upgrades, you can arrive at a structure heat loss which is considerably smaller than what was there when the radiators were installed. If you now size the boiler to the structure heat loss, rather than the installed radiation, you can end up with a grossly undersized boiler. Somewhat undersized may not be a problem. Grossly undersized, however, and you are guaranteed to have balancing problems, if not flat out no heat problems in parts of the structure -- so be a little cautious.

Really though? Picture a house getting built in 1920 with 4 rooms. Two rooms have a heat loss of X, and two rooms have a heat loss of 2X. So the total heat loss of the home is 6X.

The HVAC guy was drunk or ignorant (I know there wasn't anyone around like that in the days of steam--they all knew exactly what they were doing, but bear with me) and he sized the steam radiation in the big rooms to be 4 times larger than necessary. So they each have radiation of 8X. The total house radiation is 18X, or three times what it should be.

The HVAC guy installs a boiler sized perfectly for 18X, exactly sized for the installed radiation.

The main vents fast and each room is vented slowly to the comfort of the inhabitants and the system is working as it should, agreed? It cycles on pressure, of course, but what boiler doesn't?



Now, 100 years later (boilers lasted a long time back then of course), the current homeowner named Chris comes along and decides he wants to buy a boiler that is sized for the actual heat loss of the house. He runs the numbers and comes up with a total heat loss of 6X. He scratches his head because he knows that the old HVAC people were never wrong, but regardless, he soldiers on.

He installs a steam boiler perfectly sized for his house. This boiler is 1/3 the size of the original one. He leaves all the existing radiators and vents in place.

Does he notice any difference in comfort in any room?

No.

Because with the larger boiler, it would slowly fill the radiators according to their vent rates and the thermostat would be satisfied long before the radiators in the large rooms were filled (sound familiar?) The new small boiler does the same thing.

Did the old boiler or system even "know" there were huge radiators in those rooms? No. The vents directed the steam where it was desired.

Does the new boiler "know" there are huge radiators in the house that it will never fill? No. The vents direct the steam where it is desired.

Conclusion: There is no risk of imbalance from sizing a steam boiler correctly to the heat loss of a house, regardless of radiation installed. This isn't a new thought of course, but I wanted to take a shot at it.

GGross

Ah the new episode of "Sensitive Subjects, with ethicalpaul" just premiered
🍿

mattmia2

I think we need to see some math about what happens when steam starts condensing and pulling in more steam to take its place.

ethicalpaul

I like it @mattmia2! But in the meantime, picture those big radiators with only a few sections heated up. The steam is only in those first sections.

As it condenses, it will pull steam in to take its place, as you say. It's a constant flow.

But the vent will still only allow so much air to escape over time (with both the large boiler and the small one). The amount of sq ft of heated radiation in the room will only increase as the vents allow it. In both the old and the new, the thermostat is satisfied long before the large radiators fill.

LRCCBJ

With the larger boiler, you probably had a pressure of 1.5-2.0 psi. With the smaller boiler, you have a pressure of probably less than one ounce.

I'd be skeptical that the radiator vents will perform perfectly with pressure that low if their baseline was 1.5-2.0 psi. You probably can get to a balanced condition eventually, but it would be unlikely to see it right out of the box with the new tiny boiler installed.

You could also be in a situation where you can't purchase the precise vent that you need. A #4 could be too large and a #5 could be too small.

In any case, no contractor could take this risk. The effort to carefully balance the system could be extensive.

ethicalpaul

You could also be in a situation where you can't purchase the precise vent that you need. A #4 could be too large and a #5 could be too small.

If so, doesn't that same situation exist today? You are saying that only if you size a boiler to the home heat loss will you find it impossible to find the right vent?

Or are you saying that you might have to buy some new vents if you install a smaller boiler? OK I'll accept that.

The effort to carefully balance the system could be extensive.

It isn't today? Yet somehow we all deal with it.

EdTheHeaterMan

Based on your logic Paul, a boiler with 1X should be able to heat the home on a day in April because the heat loss for the house is much less than 6X.

That should be your next video. get yourself 3 more boilers... connect them to your system using a king valve on each so you don't leave steam from the operating boiler into the other boilers... then on a mild April day, put a can of Sterno in the combustion chamber of the smallest boiler and see how your radiators heat up.

ethicalpaul

Based on your logic Paul, a boiler with 1X should be able to heat the home on a day in April because the heat loss for the house is much less than 6X.

We all already know this, Ed, right? We know that design day is only in effect one day every 5 years or whatever and we could all get away with smaller systems on all the other days.

mattmia2

EdTheHeaterMan said:

then on a mild April day, put a can of Sterno in the combustion chamber of the smallest boiler and see how your radiators heat up.

There is a huge difference between using a smaller boiler and downfiring a boiler below its minimum design such that it doesn't produce steam.

ChrisJ

All of my Gorton vents work just fine at a fraction of an ounce. 0.15 ounce to be specific.

They aren't designed to work at a specific pressure, it's just an orifice with a valve that shuts if it gets hot. In this case, they just behave like a smaller vent at lower pressures.
All of a sudden Gorton C's and maybe even Heat Timer vents become very useable instead of being way too fast.

I have several 6's and C's in my system even on small radiators and they behave fantastic.


Even more interesting is that I have TRV's on five out of 10 radiators and them closing and opening randomly seems to have no, or little effect on other radiators. I'm sure the ones that are closed steer more steam in areas it needs to go, but there's not a disaster that happens because of it.

mattmia2

GGross said:

Ah the new episode of "Sensitive Subjects, with ethicalpaul" just premiered
🍿

if one could create a survey within an existing post I would have created one asking when I would look at the wall and see this has 138 comments and not look at it.

ChrisJ

I'm not so sure a Sterno could produce enough output to compete with the loss from the boiler it self, so it's not going to produce steam.

You need at least enough output to compensate for the piping losses plus whatever you need for the structure.

EdTheHeaterMan

ethicalpaul said:

Based on your logic Paul, a boiler with 1X should be able to heat the home on a day in April because the heat loss for the house is much less than 6X.

We all already know this, Ed, right? We know that design day is only in effect one day every 5 years or whatever and we could all get away with smaller systems on all the other days.

But there are no videos to prove your point Paul. I need you to Show Me that what you say is true. I am still amazed that you proved your equalizer point to me. Those old dead men that taught us about dimension A were fill of crap... so why did they ever come up with that stuff? and why did we all believe it for so many years? It made sense when it was explained. And the diagrams were all believable. and the pipes were not made of glass so we could see thru them. Only your magnificent video was the definitive proof of that scam!

So now you need to buy 3 more boilers to make the video! Then you can make a video in February, then one in March, then one in April. I. guess we will need to wait a year for the January one. but that is already a "known good". that would be the boiler you have now.

So if you hurry, you could complete the series before this winter is over.

ethicalpaul

mattmia2 said:

if one could create a survey within an existing post I would have created one asking when I would look at the wall and see this has 138 comments and not look at it.

You can do what I do on the threads I have no interest in--not click on them. Or maybe I should comment on all of them like you did (I mean that as a good-natured snark. I respect you.)

LRCCBJ

ethicalpaul said:

You could also be in a situation where you can't purchase the precise vent that you need. A #4 could be too large and a #5 could be too small.

If so, doesn't that same situation exist today? You are saying that only if you size a boiler to the home heat loss will you find it impossible to find the right vent?

Or are you saying that you might have to buy some new vents if you install a smaller boiler? OK I'll accept that.

The effort to carefully balance the system could be extensive.

It isn't today? Yet somehow we all deal with it.

The explanation is not relevant to the home heat loss. It is relevant to the size of the boiler versus the amount of piping and radiation that you have. The situation today with oversized boilers is that you have plenty of steam to control with your choice of vent.

When you have very little steam to work with, the challenge of balancing becomes that much more difficult.

Ask yourself why does Chris have five TRV's on the system? If balancing a steam system with no pickup factor was so simple, he certainly would not have been bothered with TRV's. Now try it with a system where the boiler output is only 60% of the installed piping and radiation. You probably can pull it off on two pipe (reference the Steam Whisperer) but on one pipe I have four words: Good luck with that.

EdTheHeaterMan

I just thought of something Paul, Why would you live is a house for 100 years, that is so out of balance with the amount of radiators that only 2 small rooms are comfortable and the rest of the house needs to have the windows open in order to let all that extra heat out in the middle of the winter? This sounds like what people in New York City do.... Not New Jersey.

Wouldn't you have removed at least 2 of those radiators my now? Your landlord must be a real @$#*

GGross

EdTheHeaterMan said:

I just thought of something Paul, Why would you live is a house for 100 years, that is so out of balance with the amount of radiators that only 2 small rooms are comfortable and the rest of the house needs to have the windows open in order to let all that extra heat out in the middle of the winter? This sounds like what people in New York City do.... Not New Jersey.

Wouldn't you have removed at least 2 of those radiators my now? Your landlord must be a real @$#*

They stayed in the same unbalanced house for 100 years because it was rent controlled. Can't pass that up!

ethicalpaul

EdTheHeaterMan said:

I just thought of something Paul, Why would you live is a house for 100 years, that is so out of balance with the amount of radiators that only 2 small rooms are comfortable and the rest of the house needs to have the windows open in order to let all that extra heat out in the middle of the winter? This sounds like what people in New York City do.... Not New Jersey.

Wouldn't you have removed at least 2 of those radiators my now? Your landlord must be a real @$#*

It wasn't out of balance. The venting made each room comfortable (just like all of us make our rooms comfortable with our oversized radiation today). The reasons things are the way they are in NYC is because the boilers are run on timers at 10psi. This is a house with a thermostat.

STEAM DOCTOR

As usual, @ethicalpaul is raising very good and intriguing points. Always good to analyze and question. This is something that has been bothering me greatly, for years. Did @gerry gill propose a similar sizing method years ago? Just to make it simple (to be honest, I did not read and study the original post thoroughly). Let's say every room in the house has the exact same heat loss. And every room in the house needs a radiator with five sections. But, due to oversizing, every room has a radiator with 10 sections. Why put in a boiler that can fill all 10 sections of every radiator? Put in a boiler that can fill the first five sections of every radiator, pretend the last five sections don't exist, and every room will have enough heat every single day of heating season??? Why not? Now this will only work, if the system is balanced. Very very balanced. If not, you can have some radiators with 8 sections  getting filled with steam and some radiators with 2 sections getting filled. If you size according to the radiators, all of the radiators will eventually have the amount of steam needed. But does seem like a bit of a waste. It seems like it's a better investment to balance the system. Which should really be done anyway.

ethicalpaul

LRCCBJ said:

The explanation is not relevant to the home heat loss. It is relevant to the size of the boiler versus the amount of piping and radiation that you have. The situation today with oversized boilers is that you have plenty of steam to control with your choice of vent.

When you have very little steam to work with, the challenge of balancing becomes that much more difficult.

Ask yourself why does Chris have five TRV's on the system? If balancing a steam system with no pickup factor was so simple, he certainly would not have been bothered with TRV's. Now try it with a system where the boiler output is only 60% of the installed piping and radiation. You probably can pull it off on two pipe (reference the Steam Whisperer) but on one pipe I have four words: Good luck with that.

Did you read my post? Or are you just arguing against it because it differs from what you may have read? Please tell me where specifically in my first post that I have made an error or there is something specific that you disagree with.

ChrisJ

LRCCBJ said:

ethicalpaul said:

You could also be in a situation where you can't purchase the precise vent that you need. A #4 could be too large and a #5 could be too small.

If so, doesn't that same situation exist today? You are saying that only if you size a boiler to the home heat loss will you find it impossible to find the right vent?

Or are you saying that you might have to buy some new vents if you install a smaller boiler? OK I'll accept that.

The effort to carefully balance the system could be extensive.

It isn't today? Yet somehow we all deal with it.

The explanation is not relevant to the home heat loss. It is relevant to the size of the boiler versus the amount of piping and radiation that you have. The situation today with oversized boilers is that you have plenty of steam to control with your choice of vent.

When you have very little steam to work with, the challenge of balancing becomes that much more difficult.

Ask yourself why does Chris have five TRV's on the system? If balancing a steam system with no pickup factor was so simple, he certainly would not have been bothered with TRV's. Now try it with a system where the boiler output is only 60% of the installed piping and radiation. You probably can pull it off on two pipe (reference the Steam Whisperer) but on one pipe I have four words: Good luck with that.

Chris originally had no TRVs.
He added two in bedrooms that are grossly over radiated and would overheat on very cold nights where run times were long.

He then decided to add 3 more to rooms for control reasons. For example, the two in the kitchen help compensate for sun gain or when the oven is in use and there's a lot of cooking going. The third is used in a drafty livingroom which is over radiated, but at times needs a kick in the pants due to a strong north wind.


My system was balanced better than most with zero TRV's. The difference in timing between radiators getting steam at their valves was in seconds, not minutes. TRV's just made the system capable of compensating for constantly changing conditions and it does very well at it.

I can cook a turkey all day long and the rest of the house stays the correct temperatures without feeding extra heat into an already warm kitchen.

ethicalpaul

Thanks @STEAM DOCTOR ! You basically got what I was saying.

Very very balanced. If not, you can have some radiators with 8 sections  getting filled with steam and some radiators with 2 sections getting filled.

This part you said is interesting. I think that what you describe with this statement will happen with any system if the "choose a vent based on the size of the radiator" method is used.

I always cringe when I hear that method...comfort in each room should drive vent sizing IMO--nothing else. This is a major takeaway from my thought experiment in this thread.

ChrisJ

Something I've said on here many times is I've found TRV's will not correct balancing issues.
TRV's will make a balanced system better but they will not fix something that's broken. Maybe if you run a ton of on / off cycles with them, but not by using a standard thermostat.


At least that's been my experience with them.

mattmia2

ethicalpaul said:

mattmia2 said:

if one could create a survey within an existing post I would have created one asking when I would look at the wall and see this has 138 comments and not look at it.

You can do what I do on the threads I have no interest in--not click on them. Or maybe I should comment on all of them like you did (I mean that as a good-natured snark. I respect you.)

The problem is that there is some useful information in there, but reading 300 comments to find it is tedious.

Jamie Hall

Just off the top of my head... without much thought... I'd say that it might be possible to get away with a much smaller boiler in such a situation with a two pipe system. It would take some effort -- and either much fussing with orifices or playing with the metering valves, if one was so lucky as to still have them. However, peripheral losses in the system -- which we can otherwise quite safely ignore -- become more and more important. The most obvious of these is losses in and around the immediate boiler area itself, but as the boiler output drops the radiation from the piping becomes more and more significant as a fraction of total power required. Not that the piping radiation is actually a loss (it isn't), but it becomes significant.

One pipe steam is another matter. While one can control how long it takes to fill a given radiator with steam at a given steam pressure at the inlet by changing the vent, unless one modifies the pressure at the inlet the radiator will, eventually, fill completely with steam or try to. If won't stop at so and so many sections. I will happily grant that while the pressure differences involved can be absurdly low, the pressure differences are critical. My first thought (and I'll have to think about this more) is that the balance between radiators would change depending on how long a boiler run was.

The obvious alternative approach to handling the periblem (if it really is a practical problem which I doubt) is to reduce the radiation in a space at the same time as you reduce the heat loss in the space -- and then reduce the boiler size to match.

ChrisJ

@Jamie Hall
A one pipe steam radiator cannot keep advancing if there's not enough steam to allow it to.

ethicalpaul

Thanks for your thoughts, @Jamie Hall! The key word in your response for me was "eventually"

yes, in my scenario, in the case of a massively long call for heat, even the grossly-oversized radiators will tend to fill up (at least as much as they are able, as Chris points out just above), but that is not nearly a typical use case.

And even if there is some imbalance when returning from a 10, 20, or 30 degree deficit, as soon as the house warms up, the very next call for heat will be back to balance (of course with details depending on things like where the thermostat is located for example).

My point overall is it's not a worry to size a steam boiler to be smaller than the attached radiation, so "size it to current heat loss next time the oversized one rots" out is where I'm at on this.

EdTheHeaterMan

@ChrisJ... Are you the Chris that is living in that Rent controlled home That @ethicalpaul is talking about? Why didn't you just take out a couple of radiators? Also I had no idea that you were over 100 years old.

jumper

"Greening Steam" talks about using radiator enclosures to limit or perhaps enhance output. Perhaps one can derate both radiators and boiler so boiler rarely shuts off. Then is pickup an issue?
If boiler is chosen for 20° outside how cold will inside get @ 0°? Of course that depends on how long a cold snap one suffers. And how many rooms does one need to be toasty? One can use space heaters in those rooms. Is that more expensive than operating a boiler that keeps whole house at 75° under subzero conditions?

ChrisJ

EdTheHeaterMan said:

@ChrisJ... Are you the Chris that is living in that Rent controlled home That @ethicalpaul is talking about? Why didn't you just take out a couple of radiators? Also I had no idea that you were over 100 years old.

You know.
I feel like I get older and older every hour anymore............

No, I don't think he's talking about me. I guess he just likes the name.

EdTheHeaterMan

jumper said:

"Greening Steam" talks about using radiator enclosures to limit or perhaps enhance output. Perhaps one can derate both radiators and boiler so boiler rarely shuts off. Then is pickup an issue?
If boiler is chosen for 20° outside how cold will inside get @ 0°? Of course that depends on how long a cold snap one suffers. And how many rooms does one need to be toasty? One can use space heaters in those rooms. Is that more expensive than operating a boiler that keeps whole house at 75° under subzero conditions?

My uncle Joe would take offense to the statement "that depends on how long a cold snap one suffers". A cold snap was good for business! So a cold snap is nothing to suffer over, it was something to look forward to. Something we all prepare for. The reason to live for. Of course my uncle Joe was also in the family fuel oil business.

The "off topic" button is second from the left.
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LRCCBJ

ethicalpaul said:

Did you read my post? Or are you just arguing against it because it differs from what you may have read? Please tell me where specifically in my first post that I have made an error or there is something specific that you disagree with.

In your first post you made the conclusion that the vent rates with the smaller boiler would be identical to the vent rates of the larger boiler (the boiler is basically irrelevant and completely disconnected from the the results at the emitters).

I have my doubts about it. I don't have the data to disagree with you but I have the sense that balancing such a system will be more difficult than you realize. The vent rates at very low pressures will likely be different than the vent rates at 1.5 lb. and the result is, by no means, guaranteed to be proportional on all vents. See the comments from Jamie Hall, above, regarding the one pipe system and the potential for varying fill rates depending on where the boiler is during the cycle.

There is some hope however. Chris has effectively done it with no pickup factor and has explained the TRV's are irrelevant.

I would like to see an actual test of this theory and how difficult it would be to balance such a system. If successful, it would change the entire approach to sizing a steam boiler!