Gus2 Posted June 16 Share Posted June 16 Hello I feel a bit of a fraud as I am not actually doing my own project, but after looking at a few forums, this one seemed to be about the best for technical advice on heat pumps, so I hope I can be indulged. Our position is we are having an air to water heat pump system installed, fully funded by government grant (so we have no choice of installer). They say they will be installing a Vaillant 5kW monobloc, a Joule 150L high gain slimline tank and 7 radiators. There is no existing wet central heating, only Fischer radiators. In their design they have used an oversize factor of 1.9. If I am reading the MCS design guidelines correctly, to be in the green zone with normal emitters the minimum factor is 2.4. They have assumed a flow temperature of 55, which as I understand it is when the heat pump is at its most inefficient, and even then according to their own figures this will be insufficient to heat some of the rooms because they will only use standard radiator sizes, ie K2 and 600mm high. I am thinking that in the future we will want to change some or all of the radiators. So in the longer term I might be looking for advice on how to go about that. In the shorter term I will be looking for advice on setting the system up, because I don't expect them to spend too much time on that. I am guessing it will be the most basic control system, so also perhaps advice on upgrading. In the immediate term, I will be looking for advice on what to look for on things like pipework sizes, etc. Link to comment Share on other sites More sharing options...
G and J Posted June 16 Share Posted June 16 Ummm, why don’t you have choice of installer? Link to comment Share on other sites More sharing options...
JohnMo Posted June 16 Share Posted June 16 1 hour ago, Gus2 said: having an air to water heat pump system installed, fully funded by government grant (so we have no choice of installer). They say they will be installing a Vaillant 5kW monobloc Ignore heat pump size for now. The system design flow temp needs to be as low as practical. At the end if the day you are the client, not the government or anyone else. The government is funding YOU via an approved supplier installer. I would be pushing for a max flow temp of 35 to 40 @ -3. Anything else is just asking for high running cost. Other suppliers out there. Just tell them NO to current design. Tell them to fix it or you will find another supplier. Link to comment Share on other sites More sharing options...
Gus2 Posted June 16 Author Share Posted June 16 The grant is administered by the local council, who have chosen this company to do the work. If we want this grant, we need to use this company. Link to comment Share on other sites More sharing options...
JohnMo Posted June 16 Share Posted June 16 15 minutes ago, Gus2 said: grant is administered by the local council Is there a reason you have to go via the council? And not direct to installer and they would claim the grant via normal channels. Link to comment Share on other sites More sharing options...
Rob99 Posted June 16 Share Posted June 16 14 minutes ago, Gus2 said: The grant is administered by the local council, who have chosen this company to do the work. That phrase always rings alarm bells with me. Which specific grant scheme is this? Just because they are funding it doesn't give them the right to impose poorly designed installations which it appears may not even comply with MCS standards. Link to comment Share on other sites More sharing options...
Gus2 Posted June 16 Author Share Posted June 16 This is the HUG Scheme. The money comes from DESNZ but it is nominally administered by local councils (although I have been unable to find anyone at the County or Borough councils who know anything about it). The admin has been farmed out to one company, who have then farmed out the actual design and installation to another company. The whole thing seems to come under the umbrella of Warmer Homes. Our thinking at the moment is that provided the rest of the installation isn't too disastrous, even if we end up replacing all of the radiators, we should end up with a reasonable system at a fraction of the cost of going the £7500 grant route. Link to comment Share on other sites More sharing options...
JohnMo Posted June 16 Share Posted June 16 1 hour ago, Gus2 said: even if we end up replacing all of the radiators, we should end up with a reasonable system at a fraction of the cost of going the £7500 grant route To give a quick example, flowing at 55 at -2 compared to day 35 at -2 would use around 40% extra electric. System design is the be all and end all of heat pump efficiency. It's super easy to accept a rubbish system then have an uncomfortable house, that's too expensive to heat. Link to comment Share on other sites More sharing options...
Gus2 Posted June 16 Author Share Posted June 16 Hi John, yes it was my understanding that flow temperature is vital to efficiency, which is why I was very unhappy with their design, but as I said, as it is fully funded (I think the grant system is different in Scotland), I think we should be able to re-work it to be more efficient for a fraction of the cost of finding our own installer and getting the £7500 grant. Link to comment Share on other sites More sharing options...
JohnMo Posted June 16 Share Posted June 16 19 minutes ago, Gus2 said: should be able to re-work it to be more efficient for a fraction of the cost of finding our own installer No issues doing that as far as I know. Everything I have seen on the MCS heat loss calcs they are over egged generally. Link to comment Share on other sites More sharing options...
Dave Jones Posted June 18 Share Posted June 18 back to the first step. Post up your heat loss calcs they have done and advise your house build type, level of insulation etc. Link to comment Share on other sites More sharing options...
ReedRichards Posted June 19 Share Posted June 19 You really ought to get a quote from a regular installer just to check that you are correct that the scheme on offer would work out cheaper. A company acting on the basis of a limited stock of radiators (which presumably they buy in bulk at a discount) rather than what you actually need does not bode well. That said, even an inefficient heat pump ought to be a lot cheaper to run than your Fischer radiators. Link to comment Share on other sites More sharing options...
Gus2 Posted June 24 Author Share Posted June 24 I am posting the heat loss calcs / emitter design they have done. The installation has started, and somre things have changed. The Hall rd is now 600 x 1000 K2. The ASHP is the Mitsubishi Ecodan 6 kW PUZ-WM60VAA, and the cylinder is now a World Heat Climacyl 180L. The cylinder is very large, I think because it has a 50L buffer in it, as well as the 180L tank. I cannot find it in the Mitsubishi literature, but I'm sure I saw on a wholesaler's website that the minimum system volume for that heat pump is only 9L, so does that mean this system is going to be more expensive to run as we will have to heat an additional 50L of water? Link to comment Share on other sites More sharing options...
JohnMo Posted June 24 Share Posted June 24 3 hours ago, Gus2 said: World Heat Climacyl 180L. The cylinder is very large, I think because it has a 50L buffer in it, as well as the 180L tank. I cannot find it in the Mitsubishi literature World heat is a different company to mitsubishi. You would need to look for World Heat. 3 hours ago, Gus2 said: but I'm sure I saw on a wholesaler's website that the minimum system volume for that heat pump is only 9L, That does not sound right, 40 to 50L is nearer There shouldn't be any radiators that are too small, ask them about why there are? Link to comment Share on other sites More sharing options...
Gus2 Posted June 24 Author Share Posted June 24 Their reply was that they only fit standard sizes, ie 600mm height K2, and the available space means that these would have to be 900mm hieight. Link to comment Share on other sites More sharing options...
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