Steam Problem

Bob Chapman

I'm trying to size up a steam boiler the building has no free standing C.I. Radiators, instead it has G.E. Air Handlers.
Model 21 FD 100D-531
10 H.P. Motor for Blowers & 2" Motorized Steam Z.V. Coil Cabinet. 30" Wide & 65" Long.
Model 21FD531 7 1/2 H.P. and same demension.

If anyone has any information, it would be greatly appreciated.

Brad White_203

How

is the system currently controlled?

How many of those Air Handlers? Any more nameplate data?

The reason I ask how controlled is that the operation would be one of maintaining a constant pressure; modulating fire might be the best way in other words, not on-off. If not modulating fire, then low-high-low would be the next best thing if you can.

"Cycled steam", as is common with radiators, will lead to cold spots between cycles given those low-mass coils.

Otherwise, the sizing would be based on an equivalent EDR or BTU capacity. There is more margin if you are "close to the size", because the volume of the coils is relatively small compared to the internal volume of most cast iron radiators. (Just keep that in your back pocket should you get to the point of being at the high end of one boiler versus the low end of the next larger boiler.)

Bob Chapman

Steam Problem

Brad
The system has a master thermostat to cycle boiler & there are 3 stories with one air handler. One motorized valve on each floor & 1 tenant controlled thermostat to control the motorized values.
2 of the units 1st.& 3rd.Floor are G.E. 21FD100D-531
Serial# 20783149 and 20783150
2nd.Floor G.E. 21FD 75D531
Serial # 20783098
There is an stmospheric gas boiler installed their right now with only and on off controll, this replaced an oil unit with unknown imput, and we believe the new unit is undersized.

Bob Chapman

Steam Problem

Mad Dog_2

Just be careful with this one bob

it sounds like a balancing problem to begin with. Mad Dog

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