ProDave

Okay there is a practical limit of about 10kW electrical power for a single phase supply, so to get the mosters, or a bank of them, you would need a 3 phase supply. If you need that much heat your money would be better spent reducing the amount of heat the house needs.

My point was, a lot of old poorly insulated and leaky houses have a heat demand that is higher than any ASHP made and yet installers still specify one with a large degree of hope. That is where you see failed installations that cannot get a house warm enough.

Last time I looked you cannot do more than 100M in one run with Cat6 so would need something half way. What about 4G mobile? If you get a good signal from three they do a very good cheap unlimited data sim.

Not true. My 5kW ASHP has been heating my house nicely here in the Highlands where we are now into the 7th consecutive week of average temperature below 0 and -16 one night (a new record in the time we have been here) Last night was -7.5 Where they struggle is in poorly insulated houses and where they have been specified too small as the designer failed to correctly calculate or measure the actual heat load needed.

@joe90 I believe your stove is ducted air in? What diameter is that pipe? Mine has an 80mm diameter inlet pipe and the duct down through the wall to the under floor void is the standard plastic extract fan ducting the flat rectangular one.

I can't see a buffer tank will change anything. That won't make it produce more heat. A buffer tank even outs the heat load for when it is running at low power when not much heat is needed. I suspect smoke and mirrors here, by the time they can get around to installing this buffer it will have warmed up, they will claim success and sweep it under the carpet, so I would only accept them trying that with a written undertaking that if it still fails to perform for the entire next winter they will look at it again. Can I ask what heating you had before and do you still have any old winter heating bills?

Isn't the fact that the extension was built long enough ago that no enforcement action could be taken by planning or building control now?

Which for my burn with a 1M drop, each 1kg/s water falling will give me 10W of electricity. It's easy to see with my modest burn and only diverting a portion of the flow would not amount to much power.

I would do the whole lot with 15mm pink fireline. If it is only a timber frame between the house and garage, that will need 2 layers of fireline with staggered joints and taped and filled or skimmed.

No insulation under the floor, I very much doubt an UFH overlay board system has "enough" insulation.

I would want to know WHY they are sloping? Built badly or subsidence? We tried once to buy a small timber bungalow with subsidence like that in one wing. Our short term plan would have been to level the floor (it would not have fixed the wonky walls or ceiling) and let it for a while with the long term plan knock it down and rebuild.

For a stove that only needs a 12mm hearth, I would insulate under it and put exactly the same floor finish as the rest of the room and just put the glass hearth on top. It is okay to draw combustion air from a ventilated under floor space it does not need any form of fan. Assuming you are not getting a glass hearth with a hole in it for the air duct, it is best to build a length of duct into the wall behind the stove to draw it's air from below.

What insulation is under the floor?

Tenants want something that "works" but importantly from your point of view that the tenants can's mess with and break. A lot of ASHP's have fiendishly complicated control units supplied with them. I can imagine if the tenants started trying to understand one of those, they could rapidly get in a mess, change some settings they should not and do not understand and stop it working. So i would suggest you do as I do, link the ASHP to a conventional central heating programmer to set the HW and heating on and off times, and put the ASHP's own controller away somehwere the tenant can't get to, like a locked plant room.

Then call them round NOW while it is cold and task them with making it work. you really don't care how they do that as long as it ends up working in very cold weather.

Hi and welcome to the forum. I am sad to say my gut feeling is whoever sized your system got the heat loss calculations wrong and the fact is, 5kW is not enough to heat your property when it is really cold. A 2001 build could be really good, or ot could be pretty mediocre. A lot of it will be how well it was detailed. Did you buy it as a design and install package? Have you gone back to the supplier to tell them it is not performing adequately?

Here is the data sheet for your thermostat https://cdn.wundatrade.co.uk/wp-content/uploads/2017/08/E02-generic-E91-touch-screen-Stat-27-4-2018.pdf See page 3. Parameter 4diF Switching differential, adjustable from 0.5C to 10C

I was about to say that. Don't even attempt it DIY if undermount, it has to look right.

So a posh electronic one? Why does it have so much hysterisis? Is that something you can adjust? Do you have a model number?

I have the same issue with the bathrooms: "Bathroom is cold" "No it's 20 degrees in there" "The floor is cold" "That's because it has reached it's temperature and the UFH has turned off"

What room thermostats do you have?

Perhaps the corrugated bitumen roof sheets don't like heat and sags in the Kentish heat of summer? (not a problem up here) I first used it on the wood shed at our previous house and 15 years on no sag and no leaks. Supported at 600mm intervals.

SWMBO flatly refused to enter an outside Dunnie while at a restaurant in Queensland, prefrirng to "hold on" until we got to somewhere with indoor facilities.

There is always a gentle slow flow of air from a bedroom to a bathroom so smells should not migrate against that. The normal is to run the MVHR at trickle speed most of the time where is should be silent, but boost it to a much faster speed when showering. Some (us) do that with a manual activated timer, others use a humidity sensor. If you are worried about wc smells, some connect a branch of the bathroom extract to the WC cistern which will extract some air directly from the pan via the flush pipe. this is known as an "odourless WC"

"designer" switches and sockets is a very good way to drastically bump up your materials cost. Personally I prefer a good well respected make of white products like Scholmore Click or Schneider. Some of the very thin "flat plate" designs just serve to show how out of true the wall is, and can look a mess, particularly when someone wants them fitted to an old house with rough plastering.