T9901075-2-3 UK
Page 6 of 38
NB
. The defrost cycle auxiliary heater should not be site enabled during commissioning on
R2, WY and WR2 systems. On R2 systems the LEV in the air curtain closes during system
defrost and defrost does not occur on WY and WR2 systems.
Point of Information:
If used, an auxiliary defrost heater may seem counter-productive for
a heat pump system. When put into context, however, the auxiliary heater fitted is of low
output for the size of the air curtain, it will just temper the discharge air and is only used for
a few minutes a day during a small period of the year. Tests at the Building Research
Establishment (BRE) test house on the heat pump air curtain system showed that even
with the auxiliary heater cutting in during defrost, as it has to during their EN14511
performance test, the annual seasonal COP was hardly affected.
The air curtain is supplied with an integral condensate drain tray fitted inside the unit so it
could be used in cooling mode during warm weather, if so desired. This should be decided
at the design stage as a condensate drain system will need to be installed if cooling is
required and extended to a suitable drain by the installer. The condensate can be drained
by gravity by connecting suitable condensate hose onto the 15mm drain pipe on the
condensate drain tray inside the air curtain. If a gravity condensate drain is not visually
suitable it will be necessary to remove condensate using a condensate pump, supplied
and fitted by the installer. The condensate pump can be located inside the right hand end
of the air curtain or in a remote location outside of the unit if required. It must be of
sufficient capacity, see Page 22, self priming and capable of providing the appropriate
suction head so the pump will lift condensate out of the air curtain, particularly if it is in a
remote location. There are two hole penetrations at the right hand end of the air curtain for
condensate pipework to pass through, see Figure 1, Page 11. Suitable condensate pumps
are Peristaltic or Rotary Diaphragm type. We recommend the Blue Diamond rotary
diaphragm type with cooling signal sensor (drainStik) manufactured by Charles Austen
Pumps Ltd. (
www.miniblue.co.uk
).
If using a condensate pump it is recommended that it has the facility so it only operates
when the air curtain is in cooling mode by detection of water in the drain tray or by
detecting a cooling differential in the airflow. It should also have a pump overrun feature to
empty the drain tray as much as possible when the air curtain is switched off. It should
have an alarm system with appropriate sensor fitted in the drain tray that will give a volt-
free signal (open circuit = alarm) and stop the air curtain cooling if the condensate drain
tray is in danger of flooding (air curtain fans will continue to operate). Other indoor units on
the same City Multi system are unaffected if the air curtain condensate alarm occurs.
There is a fixing bracket with 8mm diameter hole attached to the drain tray inside the air
curtain so a condensate sensor can be fixed in the tray by the installer. The hole can be
enlarged, if necessary, to suit the type of sensor used so it is located in the tray at the
appropriate position, see the manufacturer’s instructions that come with the condensate
pump for further information. A 230V AC, single phase electrical supply is provided inside
the air curtain to power a condensate pump and a condensate alarm connection is
provided for the condensate pump alarm circuit.
Warning:
The air curtain condensate collection system is designed to remove condensate
with the air curtain operating in cooling mode during normal summer weather conditions in
countries with a temperate climate. In case of extreme weather conditions, drain tray
blockage or condensate pump failure, which can occur, it is vital that the design of the floor
beneath the air curtain and its surface is such that it will not become slippery or damaged if
it became wet. This is similar to the conditions that might be experienced with heavy
