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Charlton Park

How a cascade heat pump system and discreet solar PV delivered quiet, reliable comfort for a new-build home at Charlton Park Gate.

LOCATION

Cheltenham

PEAK HEAT OUTPUT

22kW

SOLAR PV

JA Solar

COP

3.6

HEAT PUMP

Stiebel Eltron

EST SOLAR GENERATION

3,700kW annually

Overview

James and his family were building a new home in Cheltenham and wanted a renewable angle from the outset. Moon Design and Build brought Green Flare in to specify and install an air source heat pump system alongside solar PV. James came into the project a little sceptical, mainly about noise and effectiveness. Those concerns shaped how Green Flare approached the design.

Technology

Green Flare started with a full heat loss calculation based on the building plans. The result called for a cascade of at least two heat pumps to cover both ends of the demand curve. You need enough capacity for the 22kW peak heat load in winter, but you also need to modulate right down to 4kW for hot water without short cycling. Two Stiebel Eltron WPL25 ACS units in cascade handle that range. James chose an anthracite wrap for the units, so they'd sit better aesthetically against the house.

The solar PV system went into a discreet spot in the valley of the roof, keeping the panels out of view from the street. A 4kW array feeds a standard string inverter, making a continuous contribution to the house and generating around 4,000 units a year.

Underfloor heating runs across both the ground and first floor, working with the cascade system to keep the whole house at an even temperature through winter.

Client Feedback

James went into the project unsure whether an air source heat pump could really perform, and worried about noise for his family and his neighbours. Once the system was in, both concerns eased. He puts some of that down to how far the technology has moved on, in unit size and in noise output. He reports no noise issues at all and describes the hot water as instant and reliable. He also wishes he'd installed more solar than he did, since summer bills came in at a third of what they were in winter, and the setup works well for daytime EV charging.

"So overall, couldn't be happier with the installation... In terms of our relationship with Green Flare, couldn't be happier really. The installation was fantastic; the maintenance and the after-sales support and ongoing service requirements has been very good as well. I think overall it's been a very successful project; we've had no technical issues; we couldn't be happier with the relationship."