T9901018-1
Page 3 of 26
DESIGN INFORMATION
The Thermoscreens dry cooling unit is designed to provide up to 12kW * of dry/sensible
cooling (SHR/SHF = 1) (e.g. zero latent cooling with no condensate coming from the unit)
to areas where cooling is required but with no increase in moisture content of the air, i.e. IT
Server Rooms, laboratory areas, etc. It will do this if the room environmental conditions are
no higher than 24°C dry bulb with a relative humidity no greater than 40% and the chilled
water flow temperature entering the unit is no lower than 10°C **. The 10°C chilled water
flow temperature is set at commissioning and controlled by the Mitsubishi Electric PUHZ-
HW140 Outdoor Unit. Under design conditions the return water temperature from the dry
cooling unit is 13°C with a flow water temperature of 10°C.
* - output may be reduced if antifreeze additives are used.
** - validated by tests carried out at independent test house BSRIA, UK.
Chilled water pipework and water pump(s) must be supplied and installed to supply the
chilled water from the PUHZ-HW140 Outdoor Unit to the Thermoscreens dry cooling unit.
Hydraulic details for this installation are as follows:
Table 1
Water Volume
Flow Rate for
12kW maximum
output
Hydraulic
Resistance of
water coil in
Thermoscreens
Dry Cooling Unit at
3.2 m
3
/h
(kPa)
Hydraulic
Resistance of heat
exchanger in
Mitsubishi PUHZ
Outdoor Unit at
3.2 m
3
/h
(kPa)
Water Volume of
water coil in
Thermoscreens
Dry Cooling Unit
(litre)
Water Volume of
heat exchanger in
Mitsubishi PUHZ
Outdoor Unit
(litre)
m
3
/h l/min
3.2 53
36
15
5.1
2.5
A separate, self contained ‘closed/unvented’ water system must be used for the flow and
return water pipework between the Thermoscreens dry cooling unit and the Mitsubishi
Electric outdoor unit. This should incorporate water pump(s), expansion vessel, pressure
relief valve, filling loop, pressure gauge, automatic air vents, water dirt trap device, flow
setter valve (recommended), drain valve(s), isolating valves and union fittings for the
removal of components. The water system must be suitable for chilled water and installed
and commissioned by a qualified technician in accordance with CIBSE Commissioning
Code W, CIBSE KS9, BSRIA AG 2/89.3 and BSRIA AG 1.2001.1. For the Mitsubishi
Electric system to operate correctly the minimum water volume of the water system must
be 80 litres, so a buffer vessel may be necessary. A water dirt trap device should be
incorporated into the chilled water system to help protect the system from any
contamination and provide an ongoing indication of the system water condition. Please
note that the Fernox Boiler Buddy water dirt trap device has a hydraulic pressure drop of
12kPa (clean) at a water flow rate of 3.2m
3
/h**. If pressure drop in the system becomes an
issue it may be necessary to use a commercial type water strainer with a lower hydraulic
pressure drop. It is recommended that a flow setter valve is fitted in the water pipework
system to verify the water flow rate. We recommend the AV23 SETTER Bypass SD 20-70
l/min DN32 (Code No.223.2561.00) by Taconova
www.taconova.com
or equivalent.
For a self contained, close coupled 35mm pipework installation the following suggested
water pumps are given as a guide only :-
Wilo TOP-S 30/10 (230V/1ph/50Hz) or Grundfos UPS32-120F (230V/1ph/50Hz)
Pump selection must of course be checked by a Building Services Engineer for
each installation !
