Steam Boiler Calculator

SteamNow · September 8

@ChrisJ I think the ratio would change the larger you go. Partially based on what type of system it will be of course. But also the larger piping outputs more BTUs at a different rate that is not linear when compared to the size of the smaller piping in the smaller system.

mattmia2 · September 8

The growth of the floor area is somewhat exponential compared to the growth of the perimeter so the heat loss per ft^2 becomes less as the building gets bigger so the average spacing of the radiation becomes larger.

edit: er it isn't exponential but the ratio of outside to square footage becomes lower as the structure becomes larger.

ChrisJ · September 9

If I was trying to design a tool I'd want actual statistics of real systems in place, not speculation.

I'd also question how much this actually matters if most of that piping is fairly well insulated. The mains in my own home aren't really worth thinking about after adding 1" insulation to them. At least, that's my view on the subject.

I would be curious to see what the piping losses in an apartment building are vs a single family home.

The "NET" rating on all steam boilers is the same whether it's going in a commercial office building, an apartment building or a single family home. That leads me to believe they aren't very different.

Jamie Hall · September 9

There is, unhappily (?), a rather fundamental problem involved in all this — too many poorly characterized input and system parameters. One might hope that the errors in characterization might cancel out — but they don't.

Perhaps the best place to look at this isn't in HVAC work, but in the automotive and aircraft industry — and particularly the latter, where most parameters can be very accurately characterized. Even so, all aircraft — and automobiles and trucks — are designed and built to measure, in some way, real world results to real world inputs, and compare those to desired results, and adjust the inputs on the fly. HVAC systems respond much more slowly than, say, a Honda — but they still require some sort of real world feedback between what you want it to do and what it's doing, and a way to adjust — on the fly, in the field — the system to get closer to what you want.

Mind you, I have no objection to paper (or electronic!) analysis — but I still want to have the tuning capability.

And no, I do not have a self-driving car, nor would one work around here.

SteamNow · September 9

I agree with both of you. I went to school for Aerospace and I used a lot of those equations for predicting performance. What I'm trying to do is to use a lot of these data that is already compiled for pipes and whatnot so that I can have an actual data driven calculation. This tool I'm making is using actual data for the most part from old manuals. Except for some of the thermal calculations for the pipe heating.

I have direct access to about eight steam systems that I can basically do whatever I want with because they are owned in the family so I plan on getting some test data to see how accurate my little calculator is.

ChrisJ · September 9

https://forum.heatinghelp.com/discussion/comment/1903508#Comment_1903508

If you're using old data, you're going to get the same results everyone else has been for decades.

We have multiple members here running 0 to 10% pickups in single family houses with zero problems, actually one is running negative pickup I believe. Does this work in larger buildings? I have no idea.

But according to the old manuals it won't work in a single family house either so something isn't right.

mattmia2 · September 9

https://forum.heatinghelp.com/discussion/comment/1903516#Comment_1903516

2 pipe systems work quite well with the boiler somewhat smaller than the actual connected edr, one pipe systems can be difficult to balance if the boiler isn't at least as big as the connected edr. if something is causing the steam to prefer to go one way rather than another, it can be hard to slow it down in the direction that it prefers to make the other part of the system heat. If there is an excess of steam then it has to take both paths. In a 2 pipe system the steam can be balanced with the radiator valves or orifice plates or a combination of the 2.

i wonder if partially covering an overheating radiator would balance a 1 pipe system.

ChrisJ · September 9

https://forum.heatinghelp.com/discussion/comment/1903519#Comment_1903519

I completely forget and I'm sure you've told me 1000 times over the years, which system is in your house?

mattmia2 · September 9

I have forced air and a hot water boiler that does some supplemental heating. I just wandered here after reading a couple articles @DanHolohan wrote for Old House Journal. The oldest part of the building that I work in was built in 1958 and has steam convectors.

SteamNow · September 9

What my equations show is that insulation makes a huge difference(obviously). The analysis I'm doing for a system that I will be replacing the boiler on soon shows that with the insulation currently installed( 1" on the mains and 1/2" on radiator feed lines) the factor comes to 1.03, if you were to take out the insulation it comes to 1.4. This is in a 4 unit building with a radiator edr of 884. So the insulation lets you go down at least a boiler size. And if you go by the gross btu instead of just the sqft rating of the boiler(which has the safety factor included) you can cut it closer and just allow 10-15 more minutes for the system to fully heat the iron in the system.

mattmia2 · September 9

are you saying that the edr of the piping is 354 ft^2?

SteamNow · September 10

Yeah, without insulation that's what it comes to after doing the heat load. The Btus are dumping from the piping. Insulating it is huge.

mattmia2 · September 10

also remember that the steam can only get to where the air can get out

SteamNow · September 10

https://forum.heatinghelp.com/discussion/comment/1903465#Comment_1903465

I've done that on smaller boilers. But I'm wary to do it on a boiler so large without a combustion analyzer.

Jamie Hall · September 10

https://forum.heatinghelp.com/discussion/comment/1903557#Comment_1903557

You shouldn't do it on a boiler of ANY size without a combustion analyser. And also, on any boiler, you need to consider flame geometry when changing nozzles and pressures.

ethicalpaul · September 10

https://forum.heatinghelp.com/discussion/comment/1903464#Comment_1903464

You can put a timer relay and low pressure switch on it so that when it hits a more reasonable pressure like .5psi or even lower it will delay restarting for 10 minutes or whatever you set it to.

This will make it take longer to heat up a space from cold because at the higher pressures the temperature of the steam is also higher, but I prefer a delay reaching setpoint to running at such a high pressure as 2psi

ethicalpaul · September 10

https://forum.heatinghelp.com/discussion/comment/1903540#Comment_1903540

It's not that huge. If it were huge we could use a single pipe to heat a room, which we can't.

And beware old books, they are full of misinformation.

mattmia2 · September 10

https://forum.heatinghelp.com/discussion/comment/1903565#Comment_1903565

the difference in temp between 15 psa and 17 psa steam is small, like < 10 f degrees so changing the dt from like 150 f degrees to 160 f degrees changes the output little.