MikeSharp01

You do wonder, on the up side this morning we had a visit from our 4th potential installer of our system and he had actually done his homework, knew it was a passive class house (we may get it certified / may not) and took me through a couple of issues they had with bits of it in an intelligent and switched on way, explained the various control regimes I could have - Homely, direct, Wunda and a Vaillant system direct to their proposed ASHP which was the 3.5kW unit - the size I think we need. I also already sort of know what I want everywhere and he was happy to take me through how they might be able to accommodate, and what I might want to look at for balance - now all I need is the quote! I will let you know how that goes.

But oddly Surely not - but your observation is valuable and has resulted in my editing my post to better reflect the reality of units now.

This appears to be a very common issue - we are having it as well. The calculations, done with the Passive House Planning Package (PHPP), for our build shows we actually need about 1200W to maintain a dT of 22oC (K) (-2 OAT to 20 IAT) but we are being told we need an 8kW ASHP by one potential supplier and 6kW by others which to me is madness. However we do need to take into account the DHW needs which will need factoring into the size of the ASHP so I think I need a max size ASHP of 5kW and could quite happily live with 3.5kW.

Your'e right I should have said openable shouldn't I. Thanks for the insights the whole thing is a pain but one thing I have learned is that I like the look of the KRONOTERM heat pumps which one of the companies has quoted to fit - expensive but nice, although I have no idea of their quality / performance the do quote the sound level which seems phenomenally low. Image Source KRONOTERM documentation 09.03.2024

Yes and it's about £4k + The VAT which I will get back at the end, so as long as the quote is below around £11k then I will go with it - as long as I trust then and their technology otherwise not.

I know we, the forum in general have discussed this N times (where N is a very big number) but I thought I would start a new thread as a contemporary home for the same old chats we have had already but with a twist - see if you can spot it. We already had the discussion about having to be at least as well educated as your supplier if you want to get the system sized & designed properly for your house. I have also come across a good volume of people who have the most awful stories to tell about installations. There is also the buffer tank / no buffer tank debacle among many other things. We have been going round the houses, trying to get three quotes to do ours. Here is where we are: It's designed to be a passive house (PH) although we probably won't certify it. I did the design training and have built the whole thing around the PHPP with the architect. The Brief: We need someone to install and MCS certify, so we can take advantage of the grant, a very small list of things: 1. A UVC 2. A Heatpump 3. The plumbing for those two and our UFH which is already in the slab. 4. The controls for the above - no use of cloud systems and all systems OPEN. Background Information: (Given to all the suppliers) We already have the UFH pipes sticking out of the slab, 28mm Flow and return pipes from the utility room (UR) to the ASHP base, suitable cabling for almost any ASHP on the market from the ASHP back to the UR with room in the duct for more if needs be. The UVC will be 2.1m from the UFH header around the utility room wall. The PHPP says we need 10.288 kWh/(m2a) the TFA (Treated Floor Area) is 139.4m2 - the actual area is about 156m2 but TFA is the metric PHPP uses. Based on the above you can imagine we have good insulation - the air test is still to come but I will work at getting that well below 0.6 ACH (PH metric) SO I think I can stand by the PHPP outcome - it is roughly in line with other similar sized PH dwellings discussed on here. They all received the PHPP verification page, a full set of the Building Control (BC) drawings, the U values for the walls, the roof & slab along with the average Uw value for the window and roof-light packages (Triple and Quadruple glazed respectively) and a layout plan of the utility room showing where everything needs to go and the dimensions allowed for. To date we have had two indicative quotes (IQ) (Which are in themselves something of a conundrum because my understanding of a quote is that it is fixed - so not indicative.) The first company sent a chap to visit, he spent 10 minutes looking at the house and left - sending me a quote within 3 hours. No information about the units (brand / size / control ability / etc). The second firm we found via the famous site who seem, judging by their Youtube channel, to know their stuff and are certifying installers who take their training. They did not visit but worked off, or not, the information package discussed above. I won't share the quote but here are a couple of comparative sets of numbers to look at: First - the PHPP verification page - (True this is as designed but all the insulation is in as are the windows - just air tightness to confirm) Then the heat load response calculation by the second potential supplier on which the 2nd quote is based - How can these two be so far apart? From my perspective the laws of physics tell me that if you put 8.4kW into the house I told them about you will definitely cook it! Yet the IQ (Oxymoron perhaps) seems to want to tell me that the house is 1.5 times as big as the drawings they were sent and consumes about 2.5 times as much energy as the best estimating system on the planet for such things (other of course than the JSHarris Spreadsheet) thinks it will. They also want to fit a buffer tank and I have not allowed for this in the utility room - cos I could not see I would need one and still don't think I do! So what have I missed - like a huge heat sink / cold bridge or three that I forgot to put into the PHPP, perhaps a couple of rooms I have forgotten I have built or their assumption that with all this insulation we are still just going to let the air out via trickle vents (big ones) rather than use the MVHR which is clearly shown in the drawings and accounted for in the PHPP? It makes you wonder and so it looks to me like I need to kiss a few more frogs! Are we allowed to say such things here! I mean I don't mind if they turn into a princess or a prince I just want them to make me feel like they know what they are doing!

Yes this is what @TerryEdoes only using Willis heaters. His decrement delay, like yours & ours I suspect, is very low so it matters not that we don't run the thing full time and anyway at some point we will need to put some of the the output into the DHW - which is now going to be a UVC (or some such water filled device) because I cannot get happy, given discussions here and elsewhere, with the Sunamp unit I had originally thought I would use. Talking of DHW I have been wondering how best to control around that. We will have about 6kW of Solar so I am thinking I would want to top the UVC with that. Obviously the ASHP is the best thing to do that with, given the COP, so feed the ASHP with power from solar when the sun shines BUT once the ASHP reaches its max temperature switch over to the immersion heater fed by the Solar to give us some more stored energy.

Looking at our numbers and worrying about sizing our heatpump I cannot see a 5kW unit modulating down enough to manage a continuous delta of 5degC across our UFH a 3.5 kW might get close but is getting marginal on the DHW side of things.

Here is ours same basis - seems ok to me - its not a Passive house above 0.6 anyway. Pressurisation Test Result (ACH) Specific Space Heating Demand (kWh/m2a) Monthly Method - [Annual Method] 0.2 10.3 [10.9] 0.4 10.5 [11.1] 0.6 10.7 [11.3] 0.8 10.9 [11.6] 1.0 11.1 [11.8] 2.0 12.2 [13.0]

ooooops.

Absolutely - let's hope we here are not contributing too much - lets get back on topic - whatever that is given how far this one has wandered over 5+ pages.... Sorry @Nickfromwales

You could but you would soon either have it overwritten or asked to provide your evidence / citations/ references. I dimly recall it was compared with encyclopedia brittanica and its veracity score was similar.

only going to cause condensation if the temperature varies wildly, if it is still in its packaging then even that shouldn't be a problem.

Obviously you are not observing this meltdown at the speed of light that is happening among our elected representatives - perhaps it has not reached Cornwall yet, I mean it is light years from the center of power after all.

I guess it's all about how the contractor sees it. I have run the flow and return pipes (28mm), put in the ufh pipework, done the concrete base for the unit, pulled in a collection of cables and a few other bits. None of those quoting have said anything - while rubbing their hands with glee at less work for them to pay for.

Hello and welcome to THE forum for people like us Masood.

Yep - I am reminded of my time at Marineville - commander Shaw would calmly announce over the base tannoy that "anything can happen in the next half hour."

Couple of things. Are you digging new foundations or using the conservatory founds in which case no need to serve as I understand it. Secondly it won't matter if you digging down because the rule is circular so 3m radius.

Not the best Idea as you can claim the £7500 grant, you can still do some of the work, get the price down to the grant plus less than the unit will cost you, get it installed and commissioned for the cost of just the Heat Pump.

Interesting! Sounds like it must have something to do with the heat. Heat causes expansion so it may be that the lining, if there is one, is moving and exposing a leaky joint to a collection of water up the chimney or some such. Condensation is also a - does it ever stop if you ;eave the fire on for a long period and keep it in over night?

Yes my friend warned me of that as well.

I have almost the same shopping list - same challenges. A friend of mine, ex CISCO, said I should get a secondhand CISCO POE switch as you can get them for next to nothing, £60 buys you 48 POE ports 1Gb each at Techbuyer. Might need an expert to set it up though.

Welcome Jamie, I am sure there will be loads of ideas / support for a roof replacement. Just load them up and we can get you some answers / ideas.

Oh - OK that bad!!!!!

Hi and welcome Angus. I like to think that I can either spend time saving money or spend money to save time. I don't like wet trades - brick laying / plastering neither do I have a head for heights. So although I built the roof structure I had the slating done by others. When it comes to the plastering I won't be doing that and I hate painting so that's a job for my partner in life who, although now in financial services, comes from a long line of painters & decorators! Everything else I am quite happy to do myself and so far have on our build except fit the windows which came as a package. I will do all the electrics under the watchful eye of my local electrician and the ASHP will be done by others under the grant scheme although I would have liked to do it myself it's actually cheaper to get in a third party if you are getting the grant.