Grants available for all electric house we are buying and plan to extend. reducing Co2 emissions.

matelodave

To get maximum efficiency out of an air source heatpump you should try to keep the flow temperature down below 40 degrees.

Ours chunters away at between around 32-42 degrees averaging around 35 which is usually the temperature at which the COP is specified. However at that sort of flow temp with our underfloor heating it takes several hours for the house to respond to major temperature changes.

We don't have a buffer tank, the heatpump is connected directly to the ho twater tank and underfloor manifolds with a three port diverter valve. The 200l hot water is heated once a day to 45 degrees.

Mintyrbc

matelodave said:

To get maximum efficiency out of an air source heatpump you should try to keep the flow temperature down below 40 degrees.

Ours chunters away at between around 32-42 degrees averaging around 35 which is usually the temperature at which the COP is specified. However at that sort of flow temp with our underfloor heating it takes several hours for the house to respond to major temperature changes.

We don't have a buffer tank, the heatpump is connected directly to the ho twater tank and underfloor manifolds with a three port diverter valve. The 200l hot water is heated once a day to 45 degrees.

Do you find you run out of hot water? We have a 250l tank heated to 47 degrees 3 times a day which just covers us.....I have kids so we use loads of water.
We run our flow temp low, expecting good things from the underfloor when it goes in. Im using spreader plates rather than screed so expect the response time to be less.

matelodave

There are just two of us with no kids and we dont run out of hot water. We both shower in the mornings, but we only spend a couple of minutes each. The shower has a 6lpm flow restrictor and the taps are fitted with flow restrictors. We try not to watse water and I try to use cold where possible although my wife isn't ever so careful with it. We have a dishwasher so we dont wash dishes under the tap several time a day. In fact there's usually enough hot water left for another shower each in the evening if we want or even the next morning should we want to before the tank reheats.

The tank is activated between 04:30 and 06:30 and uses around 2kwh to reheat ( a bit less in the summer and a bit more in the winter)
We have a Polypipe overlay underfloor system laid on top of a wooden suspended floor (there's no insulation under it which I now regret as it would probably improve the heat retention). The hall has laminate floor over it, the kitchen bathroom and utility rooms are tiled directly on top and the three bedrooms, lounge and dining room are a carpeted. Interestingly we recarpets the lounge and dining room last year and insisted on low tog underlay and carpet whereas previously although it was low tog carpet the fitter had fitted normal underlay - this has made a noticeable difference to both response times and comfort in the lounge and dining rooms. be also mindful that when you cover underfloor heating) with heaps of furniture (beds, wardrobes, settees etc) you reduce the heat output of the floor

Mintyrbc

Im going for 150mm centre spreader plates between the joists with insulation underneath, involves taking the floor out but hopefully it will work well. The floors when finished will be treaded floorboards. Do you have a thermostatic mixing valve on your UFH manifold or do you just relay on the flow temp from the air source?

matelodave

No mixing valve. We've got two manifolds - a nine port one located in the hall which feeds two loops each in the three bedrooms and the hall and one loop in the bathroom - each room is a controlled zone with it's own programmable thermostat. The bathroom also has a wet  towel rail.. This manifold also has a bypass valve to maintain flow whilst the actuators open and close.

The second manifold is a seven port, feeding four loops in the lounge, two in the kitchen and one in the dining room. as all the feeds from this manifold are under the floor from this in the utitlity room it shares with the kitchen. Again these rooms are zones with their own programmable stats. the stats control actuators on the manifolds for each zone and also the heatpump and circulator.

You should note that the optimum flow temp is around 35 degrees and the rule of thumb is that it will use about 2-2.5% more energy for every degree above 35.