4.
The liquid temperature measured by the defrost coil sen-
sor must be below the defrost initiation temperature for 4.5
minutes continuously.
The defrost mode is identical to the cooling mode except that
the outdoor fan motor stops and the first stage of heat is turned
on through "66" to continue warming the conditioned space.
The defrost cycle will terminate when the defrost coil sensor
reaches 75
°
F or after 14 minutes defrost time.
NOTE: Under certain low ambient conditions normal initiation
of a normal defrost cycle may not occur. Therefore as
a precautionary measure a "Forced Defrost" is initiated
every six hours to ensure compressor longevity by
returning oil back to the sump of the compressor.
TEST PINS ON DEMAND DEFROST:
The test pins labeled "speed-up" and "defrost" are provided to
aid in field servicing of the heat pump. See Figure 11. The pins
are designed to be temporarily shorted together either by a
screwdriver or with a 1/4" female spade connector.
When the "speed-up" pins are shorted together. All timings are
speeded up by a factor of 64. This reduces the anti-recycle
compressor timer from 5 minutes to about 5 seconds and the
defrost terminate time from 14 minutes to 13 seconds: addition-
ally, the 39 minute minimum run time would be shorted to about
40 seconds or less if the system has operated for some period
of time since last defrost.
When the "defrost" pins are shorted together, the control will
allow the unit to go into a defrost cycle if the compressor is
operating. When the short is removed, the heat pump will
remain in defrost until the coil temperature reaches 75
°
F or
14 minutes expires.
If the liquid (coil) temperature happens to be above 75
°
F, the
short must be maintained to keep the unit in a defrost cycle. It
should be used since the unit WILL REMAIN in defrost until the
short is removed regardless of coil temperature. This could
cause a lockout due to high discharge pressure!
NOTE: Anytime the "defrost" shorting pins are jumpered, it
automatically resets all timing cycles. After a power
failure, all timing cycles would also reset except one
that is the 5 minute delay for compressor restart. It can
be reduced, however by jumpering the "speed-up" pins
on the control board.
INSTALLER
After installation is complete, place unit data sheet and instal-
lation instructions in customer envelope and give to home
owner.
OPTIONAL OUTDOOR THERMOSTAT KIT
The function of the outdoor thermostat kit is to prevent unnec-
essary use of auxiliary electric heat. At temperatures above the
setting of the outdoor thermostat, the electric heat is locked out
and all of the heat is provided by the heat pump.
The setting or the outdoor thermostat is important and is ideally
selected at the home “balance point”, when the heat pump
capacity is equal to the heat loss of the home. See instructions
packed with these kits.
Unitary Products Group
P.O. Box 1592, York, Pennsylvania USA 17405-1592
Subject to change without notice. Printed in U.S.A.
Copyright
by York International Corporation 1998. All Rights Reserved.
Code: SBY
515.16-N3Y (298)
