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7
Water to Water Heat Pump (WTW)
7.6.3 Water Pipe Work
Hot Water Pipework
The heat pump unit is UNVENTED. When installing
unvented hot water systems building regulations part G3
(England and Wales), P3 (Scotland) and P5 (Northern
Ireland) should be adhered to. If outside of the UK please
adhere to your own country's regulations for unvented hot
water systems.
Connect the flow for the DHW to pipe A (Figure 7.5.1).
The function of the following safety components of the heat
pump unit should be checked on installation for any
abnormalities;
• Pressure relief valve (Primary circuit and Tank)
• Expansion vessel pre-charge (gas charge pressure)
The instruction on the following pages regarding safe
discharge of hot water from Safety devices should be
followed carefully.
• The pipework will become very hot, so should be insulated
to prevent burns.
• When connecting pipework, ensure that no foreign objects
such as debris etc. enter the pipe work.
Cold Water Pipework
Cold water to the suitable standard (see section 7.6.2)
should be introduced to the system by connecting pipe B
(Figure 7.5.1) using appropriate fittings.
Negative pressure prevention
To prevent negative pressure effecting DHW tank, installer
should install appropriate pipework or use appropriate devices.
Filling the System (Primary Circuit)
1. Check and charge expansion vessel.
2. Check all connections including factory fitted ones are
tight.
3. Insulate pipework.
4. Thoroughly clean and flush, system of all debris. (see
section 7.6.2 for instruction.)
5. Fill heat pump unit with sanitary water. Fill primary heating
circuit with water and suitable anti-freeze and inhibitor as
necessary. Always use a filling loop with double check
valve when filling the primary circuit to avoid back flow
contamination of water supply.
When connecting metal pipes of different materials insulate
the joints to prevent a corrosive reaction taking place which
will damage the pipework.
6. Check for leakages. If leakage is found, retighten the nut
onto the connections.
7. Pressurise system to 1 bar.
8. Release all trapped air using air vents during and
following heating period.
9. Top up with water as necessary. (If pressure is below 1
bar)
B-228
Pipework Connections
Connections to the heat pump unit should be made using
the 22 mm or 28 mm compression as appropriate.
When connecting DHW pipes using compression fittings,
insert copper liner for DHW pipe (accessory parts) into the
pipes and tighten them from 0.75 to 1.25 turns.
Do not over-tighten compression fittings as this will lead to
deformation of the olive ring and potential leaks.
Note:
Before brazing pipes in the field, protect pipes on the
cylinder unit using wet towels etc as "heat shield".
Insulation of Pipework
• All exposed water pipework should be insulated to prevent
unnecessary heat loss and condensation. To prevent
condensate entering the heat pump unit, the pipework and
connections at the top of the heat pump unit should be
carefully insulated.
• Cold and hot water pipework should not be run close
together where possible, to avoid unwanted heat transfer.
• Pipework should be insulated with suitable pipe insulation
material with a thermal conductivity of ≤ 0.04 W/m.K.
5
0
−5
−10
−15
−20
−25
0
10
Anti-freeze concentration [%]
Anti-freeze concentration [%]
<Figure 7.6.3>
20
30
40
50
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