Air Handling Unit Temperature

Can you give some more information? Does the compressor run continuously, or does it frequently cycle on and off? What is the refrigerant, and what are the evaporating and condensing pressures? Is the air side of the coil free of accumulated dust etc.?

well these ahus are operated by absorption chiller ,and chiller is running statisfactory and providing the chilled water at a temperature of 8 degree to ahus

In that case, you may have a problem with a chilled water pump, or a control valve stuck in a nearly closed position. What are the water temperatures into and out of the AHU?

The hotter it gets outside, the longer it takes the a/c to overcome the heat load...The design temperature of the system will determine the cycling time...You can shorten the run time by increasing the insulation or otherwise reducing the heat load....

What d u mean by cycling time?and where i reduce the insulation and of what?

The reduction in heatload is not possible since we cant switch off the machines in plant during the production.

The insulation of whatever is handling the transport of the air from where it is supplied to where it is used; it is no good, clearly, if it has warmed-up again by the time it gets there.

Is this a new system? First summer it is in service?

Or, first summer you have the problem with an existing system?

Have you added equipment?

Changed the settings or any components in the system?

Lyn ----- right in the money!

This is a case of either whats changed? Load to the space, valve stuck.....

or Who sized it and what ambient load calc was used?

Hi Muhammed,

Time for the AHU to decrease temperature depends on two things:

1. Heat load in the zone
2. Heat load from outside the zone

Now in summer the heat load from outside is higher. You should do two things to sub-cool the zone before production work begins:

1. Set the AHU temperature a few degees lower.
2. Start the AHU an hour earlier.

...What might be the problem ?

Excessive humidity,undersized AHU equipment,clogged air filters,loose/broken fan belts,bad fan motor or motor starters,stuck/malfunctioing CW valve(s),chilled water coil full of air,chilled water pumps/controls malfunctioning ... I'm sure I missed a few.

Your 8deg CW temp indicates a lack of heat transfer.Because this occurs in multiple AHU's I suspect your chilled water loop(s) have circulation troubles or that your AHU CW valve(s) control system is O.O.O. (pneumatic or DDC?).

You should prolly learn more about this equipment if your to be responsible for it.

This isn't home work is it?

HTH

J