Underfloor heating and AFHP

LisselleC

We have recently moved into a converted barn (completed 2012) and I need to understand how to best use the heating system (there are no instructions).

We have 3 living rooms, a porch and a shower (electric) room/toilet downstairs, and two bedrooms and a bathroom upstairs. We have triple glazing and kingspan insulation.

Downstairs - lounge with underfloor heating; dining room with radiator; kitchen with gas AGA (cooking only) plus radiator; porch with radiator; shower room/toilet with heated towel rail.

Upstairs - two bedrooms, bathroom and landing with underfloor heating; plus heated towel rail in bathroom.

Thermostats on all radiators; thermostats in all rooms with underfloor heating.

I am used to gas central heating; I know this works differently so I don't want to end up with massive bills.

What is the best way to programme this heating system (Horseman Centaurplus C27 programmer)? The house is occupied throughout the day.

Thank you

matelodave

What make is your heating source?

Richie-from-the-Boro

Horstmann C27 commissioning and user operating instructions.

LisselleC

All I know s that it is a mitisbushi air source heat pump :-(

LisselleC

Richie ... Thank you for the programmer guide - I could only find the series 2 model guide :-)

modsandmockers

Just to be clear - the underfloor heating is electric, and the radiators are part of a gas CH system?

LisselleC

No - they are all powered by the air pump. The only thing that is gas is the AGA which is only for cooking; there is an immersion heater switch in the airing cupboard in the down position but I think this is as a back up.

modsandmockers

LisselleC wrote: »

No - they are all powered by the air pump. The only thing that is gas is the AGA which is only for cooking; there is an immersion heater switch in the airing cupboard in the down position but I think this is as a back up.

Googling around, as you do, I get the impression that your heating system is at the cutting edge of the new technologies. Have a look at this - http://heating.mitsubishielectric.co.uk/Pages/default.aspx - I think that your first move should be to contact the original installers - it seems fairly surprising that neither the vendors nor the surveyor saw any need to tell you about your property's unconventional heating system.

LisselleC

modsandmockers - Oh my word - I think you may be right! When the electrician came around on an unrelated issue he did comment on the 'Star trek' like installation in our airing cupboard. He said that 'some money has been spent in here'! The old guy that had the barn converted did so with the intention of living here himself and if you saw how the house is insulated you would be impressed.
With this in mind I really need to use the heating system to its full potential - do you think Mitsubishi would be able to advise?

matelodave

I've got an air source heat pump (not Mitsubishi, mines a Daikin and is probably configured differently to yours). You really need to understand how it's all been set up and the best way to set and use the controls.

Mine doesn't have a separate programmer as both the heating & hot water timings & temperatures are all determined by the heat-pump controller. Programmable thermostats in each of the rooms control the water flow in the underfloor heating loops in each room.

You cannot use a heat-pump like a conventional boiler otherwise your costs will be sky high. Ideally the heating circuits should be run at the lowest temperature you can get away with (mine's around 35 degrees, which is lukewarm) and on for nearly all day & night. Hot rads will cost you money.

The low flow temperatures mean that the place takes ages to warm up, so turning it off overnight means that the place will be cold in the mornings and may not get warm until late evening. Ours just sets back 3 degrees overnight so the unit is running almost continuously in the winter.

Likewise try to keep your hot water temperature as low as possible - ours is around 45 degrees C with a boost to 60C once a week to sterilise the tank. We just heat the water for two hours a day and we've got all we need for up to four showers and any other requirements. We don't waste hot water and only have short showers (4-5 mins max) with a low flow shower head (5-6lpm).

You do really need to understand how it all works to get the best out of the system. I had the system installed and so understand it pretty well but it still took two winters before I'd got it optimised and we were comfortable. We are all electric and our total electricity bill last year was just over £800

Cardew

There are a number of threads on ASHPs and the Energy Saving Trust has runs some trials.

To gain the maximum advantage of running an ASHP system you need the water temperature to be as low as possible; this is why under floor heating(UFH) is the most advantageous heating method.
The main difference between the Gas CH, that you are used to, is that you need to run the heating for long periods - even 24/7 in winter - as the low water temperature takes time to bring the house up to temperature.
Assuming the system has been installed correctly(not always the case) you should get a COP(co-efficient of performance) of 2.5 to 3.0. This means that for every kWh(unit) of electricity you use, you will get 2.5 to 3.0 units of heat.
Posts crossed!