Mitsubishi Ecodan 8kW Ultra Quiet ASHP

We replaced the gas boiler in our detached home (built in 2000) in early October. Prior to installation we improved the insulation over several years.

We started by increasing the loft insulation depth to around 250 mm. We then replaced the cold and draughty aluminium front and back doors with insulated composite types with excellent draughtproofing. Next, we replaced the single skin aluminium integral garage door with an insulated sectional type. This made by far the greatest obvious difference.

The en-suite and bathroom above the garage, despite the existing underfloor insulation, were always cool prior to the garage door replacement. Finally we just made sure all the windows seals were effective to eliminate draughts.

We chose Abacus Energy Solutions to install our ASHP. The existing gas boiler, hot water cylinder, loft tanks and associated pipework and pumps were removed. A combined 250 litre DHW & 50 litre buffer cylinder was fitted in the back corner of the integral garage along with the pumps and electrical equipment.

The outdoor unit, an 8.5kW Mitsubishi Ecodan, was installed at the rear of the house. The 4-metre pipes from this unit were encased in insulated ducting and run through the garage wall to the internal equipment.

A remote, wireless thermostat controls the house temperature that is currently located in the lounge to the rear of the house.

Two downstairs radiators were upgraded to doubles. All the work was completed in two days plus a two hour visit by the engineer a few days later to check everything and make a few adjustments.

There was very little disruption with just a few jobs for me to complete. Boxing in the few remaining pipes in my now empty airing cupboard, bricking up the hole internally and externally where the gas boiler flue was, plus refitting the lagging as I wasn’t satisfied with the effectiveness and neatness of the work. That’s me just being fussy.

It is early days yet but the system seems to be working well. Thanks to the garage location of the equipment it is very quiet; just the barely perceptible hum of the pumps is audible. The outdoor unit is very quiet too, quieter in fact than the previous gas boiler.

Due to the lower operational temperatures the days of expanding pipes ticking every time the boiler kicked in are gone.

The hot water is set at 45C and I heat it overnight on my off peak tariff. It stays hot all day due to the excellent insulation of the DHW cylinder.

The house is uniformly cozy, and is more controlled than the gas heating. I have it set at 19C from 6.30 to 22.30 and 15 degrees from 22.30 to 06.30.

Heating using a heat pump requires a change of mindset. The “run it for a few hours to warm up the house” is no more. The system is slow to respond to changes of the thermostat setting and slow to warm the house early morning, hence the 6.30 start time.

That said, having a comfortable, warm house all day is great and it suits our retirement lifestyle perfectly.

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