Installation manual
13
NOTE: N
OT
ALL
TYPES
OF
PIPE
WILL
HAVE
THE
SAME
INTERNAL
DIAMETER
,
E
.
G
.
MULTI
-
LAYERED
/
PLASTIC
PIPES
WILL
HAVE
A
THICKER
WALL
SO
THE
GUIDELINES
SET
OUT
IN
TABLE
1
WILL
NOT
APPLY
. M
ICROBORE
(8mm)
AND
15mm
PIPE
IS
NOT
SUITABLE
.
A
S
A
RULE
OF
THUMB
,
THE
EQUIVALENT
STRAIGHT
LENGTH
(L [mm])
OF
EACH
ELBOW
IS
FOUND
BY
MULTIPLYING
THE
OUTER
DIAMETER
OF
THE
PIPE
(D [mm])
BY
30,
E
.
G
. 4
ELBOWS
OF
DIAMETER
22mm
PIPE
IS
EQUIVALENT
TO
2.5m
OF
22mm
PIPE
.
NOTE: T
ABLE
1
ABOVE
IS
PROVIDED
AS
A
GUIDELINE
WHEN
USING
WATER
ONLY
. A
NY
PERCENTAGE
OF
ANTI
-
FREEZE
ADDED
WILL
AFFECT
THE
PRESSURE
DROP
OF
THE
SYSTEM
GREATLY
AND
WILL
RENDER
THIS
TABLE
INVALID
.
3.1.2 B
UFFER
TANK
The heat pump uses a reverse cycle defrost in order to defrost the evaporator by taking heat from the heating system. It
is therefore necessary to connect a buffer tank in series with the heat pump, as shown in the hydraulic schematic
diagrams (Appendix D - G). The Dimplex A-Class cylinder range come with an integrated buffer tank, which;
•
Provides some energy storage for the unit to carry out successful defrost.
•
Increases compressor life due to reduction in the number of starts.
It is recommended that a buffer with a heating element/immersion is used as it may be required if initial start-up and
commissioning are carried out in very cold weather.
Buffer Tank Sizing
For installations using Smartrads/radiators, the minimum total system water volume should be no less than 100l,
although 200l is preferred. For installations with a poor water flow rate, a larger buffer would be beneficial.
For a system with underfloor heating (UFH), the 40l buffer built into the A Class cylinder should be sufficient as the UFH
will provide enough thermal mass to limit the drop in temperature over defrost duration (provided that one zone is
always open).
3.1.3 M
ETERING
FOR
THE
D
OMESTIC
R
ENEWABLE
H
EAT
I
NCENTIVE
- UK
Please take note of the following requirements if the installation is to be fitted with a meter;
1. Leave sufficient space for appropriate meters to be fitted in defined locations.
•
For Dimplex installations using 22mm pipe, please leave 440mm of straight pipework on the meter inlet pipe and
175mm of straight pipework on the outlet pipe;
•
For installations using 28mm pipe, please leave 560mm of straight pipework on the meter inlet pipe and 175mm
of straight pipework on the outlet pipe.
2. Install low pressure-drop isolation valves to avoid the need to drain systems when fitting heat meters. See the
schematics (Appendix D-G) for more information on valve locations.
3. Leave sufficient pipework accessible, i.e. not boxed in or under floor boards, to enable meters to be fitted.
Guidelines for fitting an MCS approved meter can be found in the Domestic Renewable Heat Incentive essential guide
to metering, available on the Ofgem website: www.ofgem.gov.uk