Apartment Bldg, 4-pipe fan coil

[tlhoo]

Desiging a building with 1 and 2 bedroom units. Using Air cooled chillers and modular non-condensing boilers. Trying to select coil delta-T's for the chilled and hot water, just wanted to get some opinions. Planning to use 44F-56F chilled and was hoping to get 30F delta-T across the hot water coil, to minimize pumping requirments. Should I stick with 20 F? Any thoughts?

Thanks.

 

[quark]

30F can be ok with hot water coils but it is better if you compare the initial cost(as you require bigger coils) vs the running cost. Stick to 20F for chilled water.

 

[HVAC68]

20 deg F seems to be very high for chilled water coil. 12degF is ok. Higher delta T would mean lower flow, thereby cooling coil selection poses difficulties resulting in lower velocity and a laminar flow which affects heat transfer. The problem get compounded during part load, since water flow would further go down.

52 deg F - 42 deg F = 12 deg F

HVAC68

 

[HVAC68]

20 deg F seems to be very high for chilled water coil. 12degF is ok. Higher delta T would mean lower flow, thereby cooling coil selection poses difficulties resulting in lower velocity and a laminar flow which affects heat transfer. The problem get compounded during part load, since water flow would further go down.

56 deg F - 44 deg F = 12 deg F

HVAC68

 

[cme]

you will get better cooling coil performance with chws of 42

 

[quark]

That is a mistake from my side. When I said 20F for chilled water, I meant it is the difference between supply air and room condition but I mixed up things.

 

[lilliput1]

With (4) pipe fan coils the most you can do is total 4 rows. That is 3 row chilled water, 1 row hot water or 2 row chilled water and 2 row hot water. Check fan coil performance but I think the most you can do is 10°F T rise on the chilled water & 20°G T rise on the heating water. Make sure you use two way control valves & central bypass valve to allow diversity and not run out of gpm.