Sizing pickup factor for missing rads ? ?

Grey_Hair

Trying to size a steam boiler for an old brick 24 suite apt. Building is approx 120 years old
One pipe system, with 1525 "connected" EDR (not necessarily are they all turned on)
About 80% of the bathroom rads were removed many years ago
About 50% of the kitchen rads were removed many years ago.
About 10%+ of all connected rads have hot water wood wheel bleeders/or plugs for vents (crazy)
No vents on 2 - 4" steam mains. Has a wet return, no condensate tank.
Landlord says no one complains of not enough heat, he showed me a rad near the front entrance
which had a hot water bleeder on it instead of a proper air vent and it was hot all the
way across. There is 1.6million btu fire tube boiler, (1960 vintage) heating this apt as we speak.
My question - do you think a person should add extra EDR/btu's to the pick up factor as the new proposed boiler (WM LGB6 1607sqft steam or WM LGB7 1936 sqft steam) will be about a 1,000,000 btu's less?

EBEBRATT-Ed

Lots of variables.

Does the 1525 EDR include the radiators that have been removed?

You need the connected load x 1.33 =what you need for a boiler.

to double check things clock the gas meter or check the firing rate of the oil burner or stick the oil tank and calculate the consumption

ChrisJ

Is this a two pipe system?

How does the current boiler work?  Does it build pressure fast?  Cycle on pressure a lot?

Grey_Hair

1525 EDR is for connected rads only
This is a one pipe system low pressure
Boiler was running @ 6psi when I first saw it, it could make the 6 psi within 10 minutes when it fired up
Boiler is leaking/running bad (boiler has 61 fire tubes with 11 plugged off and 2 more fire tubes are leaking)
Amazingly still heating the building (no complaints)
My concern is - that when originally built, there was X amount of steam mains feeding the building. But because someone removed many many radiators, we still have to heat the original steam mains . . . . ? ? The 1.33 factor would be much higher if all original rads (that aren't there) were to be considered.

DanHolohan

I would use a1.5 pickup factor, after measuring only the currently installed radiators. 

nicholas bonham-carter

In your proposal, you should put a condition: replacing all the radiator vents, and installing proper main vents, as the system will no longer be running at 6 psi.
I think the over pressure has been compressing the air in the rads, so that some steam can enter, and heat the radiators.
How many floors are in the building? If you use the radiator vents with replaceable orifices, it would be easier for later adjustments of radiator venting.
The thermostat may need some change of location as well, and the end result could be a 30% reduction of fuel use.—NBC

ChrisJ

If it was me.... and it's possible, I'd fix all of the venting before changing the boiler and see what it does. Go crazy on main venting but go conservative on the radiators.

After that's all done, and the system is tweaked and balanced, see how the current boiler performs as far as timing and pressure.

STEAM DOCTOR

I would not add for the runouts/risers to the disconnected radiators. Those risers are unvented. No steam will enter them. 

AMservices

This is the kind of job that would wake me up in the middle of the night. 
Going from 1.6 M BTU down to 600K BTU is scary. 

If it was me sizing, I'd be very generous figuring a pickup factor and select a boiler that can be stage fired. Pick one that low fire matches what your current EDR is. 

STEAM DOCTOR

Insulate the mains. Unless they are being used to heat the basement. 

STEAM DOCTOR

AMservices said:

This is the kind of job that would wake me up in the middle of the night. 
Going from 1.6 M BTU down to 600K BTU is scary. 

If it was me sizing, I'd be very generous figuring a pickup factor and select a boiler that can be stage fired. Pick one that low fire matches what your current EDR is. 

These are the types of jobs I love.  Few things give me more satisfaction then installing a new boiler that is half the size of the old boiler. 

The Steam Whisperer

Yeah, we cut the capacity by more than half at my church this spring...only 1/2 the old LGB was working the past few years anyway. 2 little baby 80s at 345,000 each and a small hot water boiler at 150,000 replaced the 2,100,000 LGB.

I'd much rather see a power burner go in this application. Even with the downsizing, it is quite possible the fuel usage will go up because atmospherics are so inefficient for non staged heating applications compared to power burners. Also, the 3 foot riser requirement of the vent above the draft hood for the LGB often makes in impossible to fit in the boiler room. Using a 1.5 pick up factor is probably a good bet. If it is a power burner you can almost always cut the firing rate on a steam boiler. The LGB can be set up as two stage very easily.
I'd put proper venting in as part of the proposal too. Oversized boilers often are balancing out inadequate venting.

nicholas bonham-carter

Maybe we should start a thread, or continue an old one on the advantages, and disadvantages of of Atmospheric versus Power boilers.
A number of post here seem to show positive results with 2-stage gas valves even on atmospherics.
Whisper, I see your solution for the church was to use two staged smaller boilers, and maybe that is the solution for these apartments.
The relative simplicity of the atmospheric burner is certainly appealing.—NBC

The Steam Whisperer

This system is one pipe, my church is two pipe with zones and orificed heat emitters. The orifices help balance the heating when only 1 boiler is running, so we get good performance. So far this year, with the complete building staying at 45F or 50F, we've only used one boiler, even when it was down to 10F for a day and a half. Needless to say running 1- 345,000 input power burner boiler is going to be a lot more efficient that running a single 2,100,000 input atmospheric at the same light load. With one pipe it's a lot trickier to do staged boilers and have any significant efficiency gains. High/low or modulating power burners seem the best way to go on one pipe, unless, of course there are TRV's.. That can change everything, I would think, since many radiator will be off at the start of a heating cycle.