Underfloor Heating Systems; Pipework Materials; Condensate Disposal - Vortex Combi; Condensate Trap - Grant Combi 70 V3 User's Installation Manual

5.15

Underfloor heating systems

See Fig. 17
On underfloor systems it is essential that the return is
pre-heated by mixing flow water into the return before
it enters the boiler. To prevent internal corrosion of the
boiler water jacket, the return water temperature must
be maintained above 55°C for the Combi V3 and
Combi Max and 40°C for the Vortex Combi
Fig. 17 - Underfloor system
5.16

Pipework materials

General - Grant boilers are compatible with both
copper and plastic pipe. Where plastic pipe is used it
must be of the oxygen barrier type and be of the
correct class (to BS 7291:Part 1:1990) for the
application concerned.
IMPORTANT: The first metre of pipework
connected to both the heating flow and return
connections of the boiler must be made in copper.
If plastic pipe is to be used, the installer must check with
the plastic pipe manufacturer that the pipe to be used is
suitable for the temperature and pressures concerned.
Pipe must be Class S to BS 7291: Part 1:1990.
The boiler is fitted with a low-pressure switch to shut
off power to the boiler if the system pressure drops
below 0.2 bar.
Underfloor systems (see Section 5.15) - Plastic pipe
may be used on Underfloor systems where the plastic
pipe is fitted after the thermostatic mixing valve.
Copper tube must be used for at least the first metre of
flow and return primary pipework between the boiler
and the underfloor mixing/blending valves.
5 - GENERAL BOILER INFORMATION
Combi V3, Combi Max and Vortex Combi models
5.17

Condensate disposal - Vortex Combi

When in condensing mode the Vortex Combi boiler
produces condensate from the water vapour in the flue
gases. Provision must be made for the safe and
effective removal of the condensate.
Condensate can be disposed either internally - into an
internal domestic waste system or directly into the soil
stack, or externally - to an external soil stack, gully,
hopper or soakaway.
It should be noted that connection of a condensate pipe to the
drain may be subject to local Building Control requirements.
Pipework
Condensate disposal pipework must be plastic (plastic
waste pipe is suitable). Copper or steel pipe is NOT
suitable and should NOT be used.
The internal diameter of condensate disposal pipes
should not be less than 20 mm - e.g. 22 mm plastic
plumbing pipe or 19 mm (¾") plastic overflow pipe.
Condensate disposal pipes must be fitted with a fall of
2.5° (1:20).
For boilers installed where it is not possible for the pipe
to fall towards the point of discharge - either internally
into a waste system or externally to a gulley - e.g. in a
basement, it will be necessary to use a condensate pump.
Condensate disposal pipes should be kept as short as
possible and the number of bends kept to a minimum.
Pipes should be adequately fixed to prevent sagging,
i.e. at no more than 0.5 metre intervals.
Ideally, external pipework, or pipework in unheated
areas such as garages, should be avoided. If
unavoidable, external pipework should be kept as short
as possible (less than 3 metres) and 32 mm waste pipe
used to minimise the risk of freezing.
The number of bends, fittings and joints on external
pipes should be kept to a minimum to reduce the risk
of trapping condensate.

Condensate trap

Condensate disposal pipes MUST be fitted with a trap
- whether they are connected internally or externally.
Vortex Combi boilers are supplied with a condensate
trap to provide the required 75 mm water seal in the
condensate discharge pipe from the boiler. This trap
incorporates a float (which will create a seal when the
trap is empty) and an overflow warning outlet (fitted
with a rubber bung), See Fig. 18.
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