Undersized boiler

Snowmelt

As you guys know I’m doing work at this art school where it’s loosing water, it’s piped wrong but some people are also telling me it’s undersized I did an edr, I came under but not by much and I had two steam to air which was a guess. Also three rooms weren’t working correctly , I fixed one by cleaning out the steam trap. Now I have two rooms not working correctly, one has a leak in the baseboard steam, so that’s shut off. Other I didn’t get to yet.

My question is would a undersized boiler get the rads hot and make temperature on a 35 degree day. The only thing I have to really do is keep adding water to the system.

ratio

Depends on what the design temperatures are. I'd guess that you're still over design outdoor temp, but we use IIRC 0° around here so YMMV.

JUGHNE

Just for comparison concerning undersized boilers:
I inherited a problem job.
It is a 1953 church, 7500 sq feet on one floor, maybe 30+ foot cathedral ceiling. It has 2690 connected EDR of 2 pipe cabinet convectors. The boiler was changed out to two IN8's that produce only 1266 EDR together. The steam mains are insulated with 1" fiberglass.
This change out was in 2002. The church is maintained at 60 degrees with bump up to 65 for services.
It is cool in some small rooms on cold days.
However there seems to be no outcry from parishioners who would have no problems throwing more money at the heating system.
This is in northern Nebraska....we have some weather here!
The end of main F&T's are probably plugged, there could be bad traps...all this will wait until spring.

In your case, people who do not understand steam will think that if the heat is not getting to them then you must need a bigger boiler.
IIWM for your project I would be chasing the water loss problem down before anything else.
Again, the boiler itself....underground returns.....pipe tunnels that hide leaks, leaking coils that you do not see steam releasing, etc.

Jamie Hall

As to the direct question -- keep in mind that a boiler's EDR rating takes into account a 33% additional factor, called pickup. That's a nice margin... for a whole bunch of things.

The most important thing about it is that it is there mostly to allow for bringing the steam piping up to a reasonable temperature in a reasonable time -- and to compensate for heat loss in the steam piping once it's up to temperature.

Bottom line: if the steam piping is well insulated, you can get away with a much smaller pickup factor, and all the radiators will get hot -- though it may take a little longer, and you would need to be pickier about adequate venting (or crossover trapping) for the mains, and you certainly want to be sure you have adequate insulation on the mains and any accessible runouts.

Design day temperatures have nothing to do with it. Where design day temperatures enter into the picture is in determining whether the radiation is adequate. Or to look at it another way -- it's the radiation, not the boiler, which determines whether or not you can stay warm on a design day, so long as the boiler can match the steam requirement of the radiation -- which it sounds like you can.

Snowmelt

there are no steam pipe or returns underground, how ever the condensation pump i don't think is getting all of the condensation back because i still have a few returns that are cool. the only thing thats really odd is that the auto fill doesn't fill all the time but when someone manually feeds it and the boiler doesnt go off in low water the building does reach 70 degrees no problem.

Jamie Hall

You know, @Snowmelt , I wonder if there is a location -- either in a main or in a return -- where some of that water is hanging up and preventing either steam or air from getting to where it needs to go. An IR gun might help find a place on a main where steam stops. Less useful on a return where the water would be stopping cooler air...

Just a thought.

Snowmelt

I’m agreeing with your thinking, the one part that I don’t have hot steam is at the return part of the rads. I’ll give you a description, the steam enters from overhead, goes down to the rads, connects to three radiator in parallel on a wall, connection is on one side, then returns to other side with I think is one inch then goes to the condensation pump about 30 feet away, I’m pretty sure there might be a steam trap roughly 3 feet from the pump. But that whole return line isn’t getting warm, I’m going to disconnect both ends and run water thrue the black pipe.

JUGHNE

Is there some form of auto feeder for the boiler?
You mention if some fills the boiler manually then 70 can be reached.

If water is hanging up somewhere in piping it eventually has to return and result in an overfilled boiler that will not operate.

I had a school with this problem. It had loads of drip traps as the main was in the attic. Those traps were changed this summer. As well as adding serious air venting on the steam mains. So far no problems.

Snowmelt

Could the radiator be clogged, if so do you unclogg , would you flush it like a tankless water header?

JUGHNE

How about a picture of the problem radiators? Include all the piping to and from them in the pictures.

Snowmelt

That will be next week

Snowmelt

That was another question jughne, I don’t see any venting, in the boiler room. Does steam traps act as vents, I’m going to say no but I really don’t know, but like I said all rads get hot except for the one thT is shut off or the boiler shuts down on low water.

JUGHNE

In my school all the venting had to go thru the traps and into the dry returns. I suspected some of the dry returns to have some water standing because of bad repairs, (they are under a floor so I can not see them. )
I am fortunate to have the original blueprint from 1933 with the steam piping shown for the attic supply lines. With this plan I was able to locate where to install venting to remove air from the major steam runs.

Jamie Hall

Steam traps do not really act as vents. The ordinary radiator trap type trap does open to let air out -- into the dry return. Which means that somewhere or other the dry return has to be really vented to the atmosphere. There are any number of ways to do that, but often in larger systems with boiler feed receivers or condensate feed tanks the venting is through those tanks. That's why I mentioned that perhaps water hanging in a dry return could be the problem, by preventing the air from the radiators in that area from getting out to the atmosphere.

I am going to make a WAG that your system is vented through the returns and the condensate tank; otherwise there would be radiators which never got hot.

Note that all that applies to normal radiator traps. F&Ts are a different beast altogether, and may or may not serve as useful vents for the pipes or radiators to which they are attached, never mind doing strange things to the pressure relationships downstream from them.

Snowmelt

like I said there are only 2 rads that don't get hot ( maybe three) I fixed one on Friday, then there was one that had a pin hole leak. so that was shut off. it did get hot though.