JohnMo

If it's running for 3 hours that's not short cycling. If it runs for less than 10 mins then possibly yes.

But are pushing themselves as an installer - makes you wonder. Sounds like your heat pump is either too big, you need a buffer or bigger one, or you have the system flow constrained with too many zones closing down.

The lower the flow rate, the higher the delta T and least amount of heat from the floor. So you end with high flow temps. I have Salus self regulating actuators on three of my loops with flow temp below 30 the DT is 4 and over 30 its 7. These loops are basically 100m and the flow rates are 2.5l/min. The other 4 loops are just adjusted to give the temp in the the other rooms that I want. So bedrooms are cooler, ensuite is warmer. As said 45 flow temp is hot, 1.5 l/min is low, unless you loops are short. Lower the temp considerably and up the flow rates and run for longer. This help CoP.

Am I working this out correctly? Battery £4,826, plus install cost uplift £963 . You have 1 cycle per day if overnight charging. Warranty on battery is 10 years, but lets assume the battery is good for 20 years. 365*20 = 7300 cycles. (4826+963)/7300 = £0.79, per cycle cost for battery/install. Battery capacity can be fully drawn down, so 9.5kWh. Normal cost £0.34/kWh, so £3.34 per day at normal cost electric. Octopus Go night rate is £0.12/kWh, so 9.5kWh, so £1.14 per day at normal cost electric. Additional standing charge on split rate tariff - Octopus 0.4952, compared to a normal £0.44302, so 5p. Cost to have battery = Cost per cycle, plus standing charge = £0.79 + £0.05 = £0.84. Saving on energy cost = Normal cost of 9.5kWh - Cost to charge battery - cost to have battery = 3.34-1.14-0.84 = £1.36 per day saving or about £500/year. Without solar input and about a 11-12 year pay back. Is there a risk the battery just cancels out the benefit of the solar or visa versa? Your day time usage could be circa 10kWh, provided by the battery and in the summer by the PV, but you may need to charge the battery every day to ensure you get full benefits. Am I missing something?

I'll throw this in to the mix, as MVHR (although I have it) isn't the be all, and end all solution, for everything. Atamate_SDAR+Paper+2019+(1).pdf

Sorry but looks ugly

Have you tried bleeding?

Doesn't need pressurised treatment, but does need to be oiled to keep its colour

There's a mill at Nairn, that only does Douglas fir and Scottish larch. They may be able to help. I got larch in 4.8m lengths, so they can process good lengths.

You've used your 50 pa ach as your infiltration rate, but it's all not. It should about a 1/4 of that. You are basically adding heat loss. I would be careful with your form factor, i.e. you seem to have a big wall/roof area compared to floor area. So the likelihood of meeting passivhaus specs becomes more difficult. As said the spreadsheet as is pretty much spot on. At -9 the daily heat losses is only a couple of kWh out.

You are not included in the money loop. Your invoice just includes a credit against the total I believe, or the amount quoted to you is £xxxx, less £5k

I really would speak to the person responsible for installing, there are various things to consider I believe, roof angle, wind and snow loading etc all make a difference.

Looks like you should try a different supplier. That supplier would just charge you an extra £5k if your application was unsuccessful or the number of vouchers this year has been consumed.

If it says 0 volt it normally means 0 volt. You may fry something otherwise. If you need 240v can you take a 240v jumper of the pump contacts, if the pump is running you have a call for heat.

That's how I did my battens, there is also one horizontally along the bottom, the OSB at the top, is running cables and fixing to.

Mount the unit on a robust wall, if its to be mounted on timber frame wall (like one our units), we double skinned in 18mm ply and hung the unit directly to that. We also used Rockwool flexi in the internal stud walls for sound deadening, studs are 100mm, insulation is something like 60mm, so it doesn't touch the plasterboard. Ours is sited in a cupboard, between two bedrooms and is well oversized for it duty, so fan speed is as low as practical. You can hear nothing even in the middle of the night.

Why mess with it?

Just looked at my SAP report and for a house with a 7 ACH @50pa, the actual infiltration rate is 0.4217. So I would lower the ACH down to 0.5, instead of 1.5. that should lower your losses quite a bit. At the moment your lounge heat loss is 25% higher than my whole house, so doesn't look right.

I should have qualified my statement, but the point was the 300L buffer is huge. And depending if direct or indirect heating could be part part of the issue.

As said new boiler will be leaps an bounds better as far as kWh used. If you are replacing consider the rest of the system at the same time. A 25 year old system will be full of debris from corrosion etc. You may be better do a full re-plump or at least a power flush, then while you are at make sure the rads can heat your house at a low flow temps circa 30-40 degs. That will make the house heat pump ready, and you will benefit with even better boiler efficiency. You need a boiler that has two different flow regimes, one for hot water, the other for central heating, most can do this. But gets plumbed and wired slightly differently. Not sure doing a delta of 30 on radiators makes much sense. Most modern boilers will manage the delta T, by modulation of pump output at high flow temps mine will give a delta T of 20, at low temps a delta T of 4.

So walk us through the heat pump Do you have a buffer, plate exchanger or low loss header, or are you connected direct to the heating system? What is the flow temp out of the heat pump in heating mode? What is the flow temp going into the floor? Are all zones switched on or just one or two. How long does the heat pump run for before switching off?

Almost tropical here also - 9am this morning, still looks the same tonight. Currently -3 and due to drop to -6.

Think you may be missing the point of UFH, it doesn't need to feel warm. A radiator feel is hot, because its small surface area needs to be hot to transfer heat to the room. UFH area is the size of the room, to transfer the same amount of heat to the room it can be cool in comparison. In some cases almost the same temp as the air temp at the end of a heating cycle. Your bedroom on radiators benefit from heat transfer from the downstairs as well as getting heat from the radiators. The upstairs heating is being supplemented by the downstairs heat. Your downstairs is using 40kWh not for 2 hours heating, but really for 24 hrs, because its only on for those hours. You are really putting an average of 1.6kWh in to the floor when averaged out. Your upstairs has an average of 1.25kWh. So the same heat as a small electric convection heater for up and downstairs combined. Don't think that bad, looks quite good to me, its not a spring day, its been well cold outside. As I said two way to operate, long and slow or blast with heat, your doing the latter and as you have to run your boiler at the temp you do, its working ok for you.

How is the buffer heated - is a pressurised one heated direct from the heat pump, or are you heating via a coil in the buffer. If a coil what size coil is it?

UFH running is down to how much insulation you have below the UFH pipes and how you operate. So 150mm is good so not down to that. Heating 10s of tonnes of concrete takes quite a bit of energy, so there are two fundamentally different ways to operate the heating regime. Throw a load of heat at it over 4 to 8 hour period, just like a storage heater, then let is trickle out. This is pretty much what you are doing. So it uses a bunch of kWh in a short period. Doing this wrong you can get thermostat overshoot, which is waste full and will use more energy. The other way is a gentle flow of heat into the floor, so heat in, matches heat out, the heating period is pretty much 24/7, this entails using a lower flow temp. If coupled with weather compensation this operation can be automated. Otherwise, it can be done with a little bit of fiddling manually with the UFH mixer. As a comparison our flow temps at -5 are about 30 degs - yours 45 degrees, ours is running 24/7. Either way will use a similar amount of kWh other a couple of days. If you can reduce boiler flow temp, there are small gains to be had, as you will be condensing more.