Chilled water fan coil unit-air leaving temp. Is 21c......?

[moideen]

Dear guyes,
We have 4 no. fan coil units for super market. (New installation and new building).unit model:American breeze,ABC-20C-C1B.CAPACITY 52TMBH(REQUIRED WATER FLOW 1O GPM).pipe size is ¾” as per manufacture recommendation. Entering water temp. Is 7c.return temp is 19c.leaving air temp is 21c and room temp is 28 c (our current ambient temp is 21c!).due to high delta ‘T’. So we checked the actual flow rate is 21 gpm for two units. As per design it is ok. Cleaned the chilled water strainer 3 times.as per design getting proper fresh air(22c supply temp) We are advised by our consultant that the ‘American breeze’ is the worst unit with their experience! But my concern due to the high delta T, there is insufficient water flow, but flow meter says getting proper water flow. Any ideas, your comment and advice would be appreciated……

Moideen-Dubai

[Tesla]

The chilled water leaving temp needs to be lower, is the load matched correctly?
Or additional heat (unaccounted) being added?

[RSTC]

Are the flow and return water temperatures the same for the 4 units? Is the chiller serving other plant?

Is the chilled water pipework insulated? Is there a large dehum load?

Is there the correct air flow (what is the pressure drop of the ducting)?

[MikeHolm]

3/4" line is ridiculous for 10GPM, minimum of 1" and 1.25" is better. If it is copper, I expect they won't last too long. At that rate and Dt you should be able to move 100Mbtu but the coil appears too small for the load. Just my 2 cents.

[Brian_UK]

You say that the flow rate is 21gpm for two units, do you know what is going through each individual unit?

Manufacturers' catalogue if wanted...
http://www.americanbreeze.com/pdf/chwfancoil.pdf

[install monkey]

if ur fresh air supply is 21 is the cooling actuator closed - are you controlling off return air or actual room sensors mounted at 1.5mtr

[moideen]

The chilled water leaving temp needs to be lower, is the load matched correctly?
Or additional heat (unaccounted) being added?
FCU is low delta T design.leaving water temp. should be 13c.as per heat load unit is matched.

Are the flow and return water temperatures the same for the 4 units? Is the chiller serving other plant?
Is the chilled water pipework insulated? Is there a large dehum load?

Is there the correct air flow (what is the pressure drop of the ducting)?
insulated.if pressure drop, i thing Delta T should be low.72 story building.mitsubishi centrifugal chiller,leaving and entering is 5.5c and 8.5c.


3/4" line is ridiculous for 10GPM, minimum of 1" and 1.25" is better. If it is copper, I expect they won't last too long. At that rate and Dt you should be able to move 100Mbtu but the coil appears too small for the load. Just my 2 cents.
as per catalouge pipe size is 3/4".

if ur fresh air supply is 21 is the cooling actuator closed - are you controlling off return air or actual room sensors mounted at 1.5mtr
now lowest ambient temp. is 15c. so fresh air is controlled.otherwise it will affect other shops and apartments. shop is in ground floor, nearest all shops and resturants(Mc donald-installed oven.....etc) getting proper cooling.


Moideen-Dubai

[nike123]

Did you correctly and thoroughly purged air from fan coils? Are they have automatic air vents?

[moideen]

Did you correctly and thoroughly purged air from fan coils? Are they have automatic air vents?

it doesn't automatic purging line, but has common purging line, anyway my next visit to the sit will be checked.

[goshen]

Hi
check your piping ,are the valves 3 way or 2 way,look for crossed pipes and wrong connections ,
the delta t you gave here corresponds most probably to crossed piping .
good luck

[moideen]

Hi
check your piping ,are the valves 3 way or 2 way,look for crossed pipes and wrong connections ,
the delta t you gave here corresponds most probably to crossed piping .
good luck
2 way valve,connection is ok.any way rechecked on monday......
thanks to all their response
moideen

[Brian_UK]

Hi
check your piping ,are the valves 3 way or 2 way,look for crossed pipes and wrong connections ,
the delta t you gave here corresponds most probably to crossed piping .
good luckGood point, had that with half of the piping at Sharjah airport many years ago.

[install monkey]

is all the pipework in 3/4 or just the braches to each fan coil? is each flowrate correct to each coil?

[moideen]

is all the pipework in 3/4 or just the braches to each fan coil? is each flowrate correct to each coil?
header 1'' and branches 3/4

Good point, had that with half of the piping at Sharjah airport many years ago.
hi brian, can you please explain

[install monkey]

So we checked the actual flow rate is 21 gpm for two units. As per design it is ok. Cleaned the chilled water strainer 3 times
why was the strainer cleaned 3 times- was there a constant accumulation of crap? your flow rate of 21 gpm on 2 units-what was the flow rate on each unit on the system, is the main pipework lower or higher than the fan coils ? just incase there is air in the coils

[Brian_UK]

Hi Moideen,

Sharjah Airport had a section of mains pipework that transferred from one side of the building to the other. In the process they managed to cross over the flow and return pipework.

The filters were getting blocked on the wrong side and the coils and control valves were picking up all the dirt before the strainers.

Lots of sand inside the pipework which will take years to get rid of.

[nike123]

Dear guyes, We have 4 no. fan coil units for super market. (New installation and new building).unit model:American breeze,ABC-20C-C1B.CAPACITY 52TMBH(REQUIRED WATER FLOW 1O GPM).pipe size is ¾” as per manufacture recommendation. Entering water temp. Is 7c.return temp is 19c.leaving air temp is 21c and room temp is 28 c (our current ambient temp is 21c!).due to high delta ‘T’. So we checked the actual flow rate is 21 gpm for two units. As per design it is ok. Cleaned the chilled water strainer 3 times.as per design getting proper fresh air(22c supply temp) We are advised by our consultant that the ‘American breeze’ is the worst unit with their experience! But my concern due to the high delta T, there is insufficient water flow, but flow meter says getting proper water flow. Any ideas, your comment and advice would be appreciated……


According to your data:

Flow for two units is 21 gpm or 5,8 m3/h if unit is UK gpm.
Δt at water side of both units is 12K (19°C-7°C)
m=cca 5800kg
Q=m*1,163*Δt

Calculation say that 2 of your fan coils together are collecting 80,95 kWh of heat, and according to catalogue data, their capacity is 15 kWh each.
So, something is probably measured wrong (flow probably) since there is no way that coils could collect that excess amount of heat.

I would say that your actual flow is more likely 8 gpm (UK) for both units (4 gpm each).

You should carefully measure flow and temperatures at individual units.

How did you measured your flow? What instrument, what procedure.

I like installing this in new installations:
http://www.caleffi.fr/en_IT/Technical_brochures/01166/01166.pdf

[MikeHolm]

I doesn't say but I wonder how they would work with Grundfos or Wilo ecm pumps that move around on the curve.

[nike123]

I doesn't say but I wonder how they would work with Grundfos or Wilo ecm pumps that move around on the curve.


You should set these pumps to work with constant differential pressure.

[multisync]

Is the water circuit a loop with a choke valve ?

I would fit a flow meter on the return port of one of the ahu's and read the actual flow rate through the unit then take the DT.

pictures and diagrams always help from this distance..