I have a large (>1,500,000) medical facility that has a plate and frame heat exchanger in parallel with four other chillers. The cooling towers are split with one bank serving two of the chillers and the other bank of cooling towers serving the remaining chillers and the plate heat exchanger. This was done so that the plate and frame could be used to pre-cool the chilled water when the outdoor air wet bulb is low but yet too high to carry the whole building or when the cooling load is greater than that of the just plate alone. The plate is sized to equal the capacity of the chillers. All four chillers are 1250 ton centrifugal units and the plate was sized for the same capacity. The plate and frame is design to sequence to the first position whenever the outdoor wet bulb temperature drops below a preset of around 48?F and produces around 46?F chilled water supply temperature.

I am in the process of updating our existing model of the facility that was built prior to the addition of the plate and frame. I am looking for some advice on using the equipment controls and load management functions of Equest. Specifically how to change the sequence when the wet bulb temperature drops below the setpoint that enables the plate to operate as the lead ?chiller?.

Also, has anyone specified the capacity curves for a plate and frame heat exchanger? I have done this in the past for chillers but not a plate. Any ideas or experience?

Thank You,
Jason Moody, PE