Dimplex ACCHYPK User Manual

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4.1.2 Buffer 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 (Appendices). 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

The minimum total system water volume (including water in heat emitters) should be no less than 100l.

Water volume in pipework, heat emitters and the built-in 40l buffer tank included in the A-Class cylinder

must all be taken into account. This is particularly important when using Smartrads, as their water content

is low compared to standard radiators (0.6l for SRX180 model).

4.1.3 Adjusting the spring loaded by-pass valve (if tted)

CAUTION: If an externally controlled zone pump is connected when using any schematic, the spring

loaded bypass must not be used and instead must be replaced by an open bypass tted with a gate valve.

This is to ensure that the zone pump(s) is/are not running against a dead head when the heat pump is idle

or in DHW mode

The bypass valve is used to maintain a minimum ow rate and prevents faulty operation of the heat pump,

as well as allowing it to run efciently. The bypass valve must be adjusted correctly after commissioning

the heat pump.

Please ensure that the following steps are taken when adjusting the bypass valve;

1. Ensure that the bypass valve is open fully and begin running the heat pump.

2. Close all of the heating circuits that may be closed during the operation of the heating system so

that the least favourable ow rate can be achieved. This should cause all of the ow to go through the

bypass valve. To check that all of the water ow is going through the bypass valve, feel the pipe after the

valve to check its temperature (it should be getting heat from the heat pump).

3. Slowly close the valve until the water is no longer owing through it, then turn the valve back

slightly (approx. 0.5 to 1 turn) to allow some ow and prevent the heat pump from tripping.

4. Open the zone valves while the heat pump is still running, and again check the ow through the

bypass valve by feeling the pipe after the valve and checking its temperature (it should not be as hot as

ow temperature). The bypass setting should allow hot water to ow through the bypass valve when some

of the heating circuits are closed.

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Dimplex ACCHYPK A-Class Hydraulic Pack