Paul Ashley

Thanks for your replies - apologies for slow response, I have been away. jayc89 - manifolds to furthest rooms around 10m, the flow/return supply pipes are insulated for the 20cm I can see then they disappear into the concrete, yes I have measured the flow/return temps - in very cold weather (sub-zero) they are around 30/25, I don't have a heat loss calc to hand JohnMo - understood but that doesn't explain why the en-suite (tile floor) is colder than carpetted bedrooms next door. I'm thinking of (1) improving insulation (2) add wall heater if needed. Definitely don't want higher flow temp due to the COP hit as you say Nickfromwales - yes oil system did keep it hot. Not surprising - my neighbour is still on oil and has same UFH system. His flow temp is about 75C so no wonder! Oil tank is long gone. I do have room to add another heat pump for far end of house but I think that's a last resort after insulation and timed wall heater in en-suite first and lower tog carpet/underlay. Question on weather comp - Midea heat pump set to 55C at -2C and 37C at 15C on weather comp. Does that mean that my changing the flow temp on the controller overrides this?

Good evening New to this site but already found some great information - thank you. I have inherited a UFH system, which when we bought the house, was run by oil-fired boiler. Semi-rural with no gas feed so switched in 2022 to Air Source Heat Pump. This is used for DHW and heating. The property is a large barn (approx 350m sq) which is long (40m) and mainly on 1 floor. There are rooms upstairs where former loft space has been converted to living accommodation. UFH is downstairs, radiators upstairs. Upstairs rooms rarely used especially in the winter so the heating system is not usually on upstairs. Due to size of property, we have a 16Kw ASHP with 2 sets of manifolds. One serves the kitchen, utility, dining room, hall and study. All of these have stone floors. The other set of manifolds serve the bedrooms (3), hall, lounge and 2 bathrooms. Lounge is engineered wood floor, bathrooms are tile floor and bedrooms and hall are carpeted. I believe the tog on the carpet is 2.0 and the underlay is 0.6, which I know is way higher than efficient. This is a problem in sub-zero weather due to a combination of the main bedroom having carpet, being the furthest away from the heat pump (40m away) and SW-facing, so there is a cavity wall but no cavity wall insulation. I believe there is internal insulation but nothing in cavity due to cost of specialist foam fill when built. I am trying to get my head around what is the most cost-efficient way of improving the UFH performance. At one end of the house, it's fine. Performance from the other end is poor. In sub-zero temperatures, it's impossible to get the main bedroom and en-suite above 15C. A bit better each time you move towards the ASHP and manifolds, so 18C for next bedroom and 19-20C for lounge is doable. The ASHP can definitely produce hot enough water for the system at 0C external temp as input/output temps when driving the radiators are easily 55/52 when asked to deliver. Same for DHW. Input/output temps on UFH though can be more like 35/31. This I don't understand. Why such a huge difference? Am I really losing that much heat by sending the water around the UFH system and if so why? Can someone explain what the system does with the water that's being requested at 55C and why the flow temperatures are so low? It is quite clear that in order to hit my target temps in each zone, I need a flow temp (as read from the flow thermostat on manifold) of around 40C and I just can't get that. I'm thinking that the assumptions (eg about insulation levels in floor and walls) made by the person who did the independent survey pre-ASHP installation, were just plain wrong. What can I do and what would be most efficient and cost-effective? Considerations are - specialist insulation in end wall of house (which gets all the wind and rain), take out carpet in bedroom and replace with something better for UFH, add another heat pump just to deal with end rooms to reduce burden on main system or switch end rooms to radiators rather than using UFH at all. Where do I start? Any help appreciated. I'm not technical at all so need things explained logically and simply Many thanks