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Living with an Air Source Heat Pump - Part 2

Heat Pump Survey Sizing and Ordering


Miss Part 1? Read it here.

What size of heat pump?

To size our heat pump I put our house through Ecoliving's standard surveys and energy / heat loss calculations. These standards and processes are largely dictated by the Microgeneration Installation Standard (MIS), 3005 for Heat Pumps, but also by Ecoliving's own business and quality processes. As a Microgeneration Certification Scheme (MCS) accredited installer, MIS 3005 is the minimum standard that Ecoliving works to on heat pump installations.Roper_wholehouse_Blog

The initial survey captures details about the property and the owner's patterns of energy use, including: property age, size, construction characteristics, insulation levels, existing heating and hot water system, and current energy bills. This information is fed into a whole house energy calculator which also takes into consideration geographical location and climate data. The key outputs of the calculator are: an estimated heat loss, annual energy use and recommended heat pump sizing.

In our case initial output was a property heat loss of just over 10kW at the outdoor design temperature of -1.5oC (sizing the heat pump to use compressor only, without backup heater use, for 99% of the year).  Our estimated annual energy requirement for heating and hot water was 40,000 kWh, with an input fuel requirement for a suitable air source heat pump of between 13,500 and 15,000 kWh.

Which air source heat pump?

There were a range of options available to me from Ecoliving's selected heat pump partners: a 14kW Mitsubishi Ecodan; a 14kW Daikin Monobloc; a 14kW NIBE 2025; and a 12 kW Dimplex LAMI. In the end I opted for the Dimplex because of its good fit to the capacity required, compatibility with my existing electrical supply, inverter driven technology and the competitive price point of Dimplex's heat pump and cylinder package.

I opted for a 300l hot water tank to supply my family of 4, which is more than I would normally recommend for a similar, typical customer, but we quite regularly have family and friends to stay and I wanted to be cautious.

The detailed survey

Having carried out the heat pump sizing and decided on a model, I then produced an initial estimate which I (as the customer) decided was acceptable and hence proceeded to the next part of our process - to carry out a detailed room by room survey of my property. This involves assessment and measurement of every room, wall, window, door and radiator in the property; which in turn feeds our room by room energy calculator. This tool provides a heat loss and energy star rating for every room, as well as a recommended radiator sizing (if using radiators). This radiator sizing is compared with the current installation to confirm if any rooms are likely to be under-heated; which in turn prompts a discussion with the customer as to whether any radiators should be upgraded.


I had this radiator discussion with myself and decided to upgrade 3 radiators, 1 of which was already undersized for our existing oil fired heating.

The detailed survey also provides a more refined energy performance for the property and in our case the estimated heat loss dropped down to just over 8kW, with a correspondingly reduced annual energy requirement of 25,000 kWh, an input fuel requirement of 9,000 kWh and an estimated annual bill of £1,100. To provide the same energy output from oil would cost in the region of something like £1,715.

The quotation and order

Following the detailed survey I produced a final quotation and order pack which I sent to myself!
I signed the order confirmation, paid my 25% deposit, submitted the Renewable Heat Premium Payment application form, agreed a date and sat back while the other me got busy organising the installation.

Written by Ecoliving at 10:03

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Ecoliving is a specialist provider and award winner of micro-renewable energy solutions - heat pumps, biomass boilers, combined heat and power (CHP), underfloor heating, solar and wood burning stoves. We also offer service, repair and maintenance.

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