Mitsubishi Electric ecodan PUHZ-W50VHA2 User Manual page 49

Underfloor heating
Heat pumps provide lower flow temperatures than traditional gas fired boilers, this means that the installation conditions and heat
emitters need to be managed carefully. These lower flow temperatures suit the conditions required for under-floor heating
systems and if installed and designed correctly can deliver a more comfortable, consistent temperature whilst also increasing the
efficiency. Some points to note when designing the installation are :
Room by room thermostats ensure adequate control in all rooms
Temperature difference across the flow and return should be less than 10ºC (5ºC for the Ecodan)
Use of night-set back instead of turning the system to off, reduces the desired temperatures by around 3-4ºC from their
daytime levels if desired
However, response times from underfloor heating are much slower than radiators and therefore the property will take
longer to heat up making this type of system less suitable for timed heating cycles
Any additional radiators should be sized on the flow temperatures used for the under-floor heating, this negates the need
for mixing valves, which are detrimental to the efficiency
When specifying under-floor heating there are some important factors to be aware of, as rectifying mistakes will be costly if not
impossible.
Bad placement of thermostats, where they are affected by external sources of heat or cold temperatures will lead to poor
temperature control.
Under-floor heating circuits can produce high pressure losses. The pumps provided in our packaged systems are capable of
providing the necessary flow rates on averagely sized primary circuits, but with the inclusion of under-floor circuits
additional pumps will probably be necessary and potentially a low loss header to ensure the flow rates remain high across
the heat pump.
The output (W/m
pipe centres, resistance of floor coverings. If these factors are not considered at the design stage then the output may not
be sufficient at the desired flow temperature negating the benefits of using under-floor heating systems.
Resistance of floor
Spacing distance
SYSTEM SET -UP
Flow temperature set for under-floor
2
)of under-floor heating is primarily affected by 4 things: pipe diameter, length of circuit, spacing between
covering
Flow temperature too high, mixing valve required
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