MortarThePoint

I've installed UFH upstairs and downstairs so should be able to dissipate 11.2kW with a flow temp of 35C or a bit above. Is short cycling when it turns on for a short duration? I imagine that is influenced by the allowed temperature swings on the thermostats. Is that correct? If so the cycle on time would be the same if I allow proportionately larger temperature drops. All my options are the same size I think. Vary between brands though.

The hour figures are simply outputs that show how long the ASHP needs to be on for at 100% to provide the required energy. It could be run at a lower setting for longer if that is desirable. I have done a basic thermal time constant model that suggests the house will cool down (i.e. loose heat unheated) at a rate of 0.1C/h when it is 4.2C outside (so dT = 14.4C). The cooling rate is 0.07/h or the time constant is 144h (6days) (half life 4.2days). With 11.2kW I'd almost be able to only run the ASHP during E7 electricity and only suffer 1.4C temperature changes. I know the COP would be worse as colder at night, but the electricity is cheaper. I don't fancy making a 60kWh battery at the moment to allow the electrical demand to be spread across the day. I know this already from the SAP: Total Fabric Heat Loss 234 W/K (A) Ventilation heat loss (max): 138 W/K (B) Heat transfer coefficient (max): 372 W/K (A+B) If AT=4.2C and indoor is 18.16C then average power requirement is 372W/K * (18.16C - 4.2C) = 5.19kW if there were no solar/metabolic/appliance/etc gains. In December the solar gains seem to average 0.47kW and the internal gains are about 1kW. 5.19kW - 1.43kW = 3.76kW SAP has a monthly space heating demand for December of 2774kWh: 2774kWh / (24h/day * 31days) = 3.73kW Water heating is shown in the SAP as 220kWh/mo so that averages to: 220kWh / (24h/day * 31days) = 0.3kW. In theory I could have a smaller ASHP, but I would want extra grunt for when it is unusually cold. 8KW would suffice (down to AT = -11C). Other than capital cost, what is the main downside of having too big a unit? Do you mean Jeremy's Spreadsheet?

Dimensional comparison:

I think I'm more drawn towards the Ecodan due to its proven track record. If I needed 14kW it would be a different matter. My SAP shows a peak monthly heat demand of around 2700kWh in December with an average outside temp of 4.2C. that works out as about 90kWh/day so about 8 hours of 11.2kW (3.75kW average). That's with an indoor to outdoor dT=18.6-4.2=14.4C. If outside goes to -5C then dT=23.6C and that would make for 90*(23.6/14.4)=150kWh/day so about 13hours of 11.2kW (6.1kW average). There would be an additional hot water demand but pretty low (max. 300kg * 50C * 1Wh/kgC = 15kWh so about 1 - 2 hours worst case). Bear in mind that would have to be a day with average temp of -5C which where I live is unlikely.

The 11.2kW/12kW units are very similar in quietness (47 vs 46), but the Samsung 14kW units are a fair bit quieter than the Ecodan units.

Samsung have come out with an interesting looking new ASHP, EHS Mono HT Quiet, R32, Heat Pump, 12.0kW. Also available 8kW and 14kW. Available single and 3-phase. Unlike with Ecodan/Zubadan the 14kW unit is the more standard 1m height which could be a big win for people who need a little extra power. Prices look similar. Black in colour. They have a headline COP figure, but then give power out and power in data at varying FT and AT: On first inspection the COP looks worse, as at most ambient temperatures the resulting values are lower. However, at the key temperatures in the South of England, they have done a better job of optimising the design and get better numbers (suspicious?). Red is the better: 14kW model has similar COP numbers in the 2C to 12C range (1% worse than the 12kW model): The basic linear model makes for average COP values of 4.41 at FT=35C, 4.05 at FT=40C and 3.68 at FT=45C. That's about 2.4% better than the Ecodan figures, but the linear model doesn't fairly represent the improved better optimisation of the Samsung (e.g. 9% better COP at AT=7C). The Ecodans have been around for longer, so perhaps there are some optimisations not reflected in their data. There's more in field experience for the Ecodan which is a plus.

The soppy can works fine. Looks like I have a load of duff cans

A reasonable formula for the COP of the Ecodan 11.2kW is COP=(0.521 - 0.0068E*FT)*AT + (4.44 - 0.0485*FT) where AT is the ambient temperature and FT is the flow temperature, both in C. Using that I get my expected average COP based on the flow temperature with the assumption that the flow temperature stays constant throughout the heating season: COP = 7.47 - 0.088*FT That assumption feels reasonable given most of the demand is across 3 months with an ambient temperature within 1C (DEC-FEB) and the rest is mostly still within an ambient range of 2.8C (NOV - MAR).

I have found a databook from Mitsubishi Ecodan and here is some performance data for their 11.2kW unit: https://library.mitsubishielectric.co.uk/pdf/book/ATW_Databook_R32_2020#page-60-61 Based on my SAP and that data (nominal), I should achieve (my model) an average COP of 4.34 with a flow temp of 35C or 3.45 with a flow temp of 45C. Having put in UFH upstairs as well as downstairs, I will hopefully be able to use the lower flow temperature (UFH power output W/m2 data below). This all ignores domestic hot water, but I'm OK with working out the space heating needs as a priority. Modelling as linear above 2C ambient would have been fine. Here's UFH heat output vs flow temperature: data from link below except red which is from a good linear fit. https://www.tradingdepot.co.uk/info/plumbing/polypipe/underfloor-heating-heat-output-tables/

It was in the house we're currently living in so temperatures were OK. I'd be surprised if it went above 25C

Temperature range was fine, but they were on their side as packed by supplier. All dated mid to end next year. Arrived in May this year (5 months ago)

I have 6 and have given each one a shake. Two make a lot of slopping sound where as the rest bearly make a sound. I'll try a sloppy one.

Do new cannisters of FM330 normally make a slopping sound when shaken. These don't but I presume that's because they are completely full. I did manage to get a trickle of FM330 out of the older gun.

One gun is brand new. Both sprayed cleaner ok. Yes, unscrewed until it fell out.

I've bought some of this and am unable to spray it with my normal foam guns. One is an Everbuild P65 and the other is a no-name Amazon foam gun. Do you need a special gun (e.g. from Illbruck) or do I have a duff batch of foam (still well in date code).

I suspect I have over done things a bit, but it should be OK. I pushed the Isokern adapter onto the pumice and it seemed firmly attached by the rope friction. I made sure it was level in both directions. I then added a support either side of the adapter that barely (if at all) touches it but would stop it dropping down. This support proved useful for two other purposes. I hung the cut to length vitreous pipe from the support as I slid the stove in and having then lowered the pipe into the stove, cemented it in place. I've been concerned about the steel lintels getting hot, so I then wrapped the pipe with fire blanket (25mm) and put some additional A rated APR insulation in there to keep the heat away from the lintels. The supports helped constrain the bio soluble fire blanket. A makeshift 'register plate' made as two halves out of 3mm aluminium finished it off.

Sounds great. That's the unit I'm considering, but I'm tossing up between 3phase and single phase. 3phase is £500 extra. Programming the controller scheme or were there other aspects to look out for?

What model ASHP do you have?

Just spoke to someone at Scheidel and the spigot on the adapter is 100mm long anticipating the flue pipe being cut short to allow it to be slid up allowing stove to be slid under. That should make it easier. I confirmed that no sealing is then required at that junction, so it will be allowing expansion. I didn't ask, but that would make it important to hold the adapter in place as could fall down otherwise opening a big gap. The technical guy said that no rope or cement is needed with the adapter as it already has a rope tape inside. @joe90 your setup sounds more belt and braces and clearly works well. I think I'll follow the recipe of the phone call though as my stack up is: Stove 5-6VIT vitreous adapter to mate 6" pipe to 5" stove outlet 6" vitreous which I need to cut to size Isokern adapter 6" to 175mm Isokern support block I've bought some 3mm aluminium sheet cut to size (2 halves) to make a plate to go around the pipe. I still need to cut the pipe hole (semi circle in each half of the plate) which is unfortunately going to coincide with the pipe's door, but can't be helped.

Where did you allow for expansion? You have glued the adapter to the pumice, did you need to pack it with any fire rope? What glue did you use or was it just 'fire cement'?

What did you go for in the end. I'm at 11.2kW so a little lower, but a 3phase is quoted to cost £500 more than the single phase of the same model. Like you, I will have 3 phase power either way.

Fair enough, but we are in odd times and am I going to be able to get a new tariff like that (i.e new customers)? Personally, I can't have grid gas anyway so the toss up is vs oil for me which is around 90p/l -> 90p / (10.35kWh/litre * 85%) = 10p/kWh of heat Assuming an oil boiler efficiency of 85%, I need an SCOP of 2.9 or higher presuming I can get the 34p/kWh electricity tariff.

I don't understand the 'is an ASHP cheaper to run' problem if using it with UFH on the correct centres. If there was a large non-linearity in it's output (i.e non-flat efficiency curve) then it would make sense. Unless you need power past the tipping point, the problem can be overcome by duty cycling can't it. ASHP plus radiators, that's a different matter. Without savings associated with E7, ASHP has been and will be* more expensive to run than grid gas for all houses won't it. [* for a while at least] Is it worth installing, that's harder to understand as you need to offset the capital cost.

I'm surprised your indoor temperature is so constant during the day without the heating on. Do you have lots of glass and solar gain? It starts to drop at 9pm at a rate of around 1C in 5 hours.

Interesting. I think taken over such a long time the effects of solar gain mask the most interesting bit. Do you have that for just January 2022?