sharpener

Yes, I had to add a relay to mine so the weather sensor is open circuit when cylinder calls for heat, seem daft they didn't build this into the boiler. I knew there would be a catch with HPs, it seems there always is! Yes, I have proposed a TS also. It would go in the same space in the utility room as the replacement cylinder and I would rather spend the money that way. But as posted elsethread I can't get Vaillant tech to agree it, they have sent me a "TS" schematic but it is basically the same as their buffer scheme and has nothing to control when it charges/discharges. Given that I think the only real problem is that Part L and MCS require weather comp so the installers won't allow any space heating which disables it.

It occurs to me that a contributory factor is the typical HP mfrs' scheme with DHW priority and a full-flow diverter valve, which means all the output has to go to the cylinder. Gas/oil boilers aren't installed like that, often S-Plan. If instead you had just a single circuit at 55C then it is likely that at any one time some of the rads will be calling for heat as well so the HW coil will not have to absorb the full output. (Any UFH would of course go on a different circuit designed for a lower flow temp.) In summer you might have to fall back to resistive heating from PV which is hardly a disaster, or at worst E7. I will put this to my potential installers and see what they say, though I suspect the answer will be "it is not in the Vaillant schematics book". FWIW Grant do market their HPs as a drop-in replacement with S-plan plumbing which might make it a bit easier with them.

Thanks, wasn't imagining it then! Can't find it by browsing Stelrad site though, even searching today for "radical". Wolsely don't have them available for online purchasing but say they may be obtainable to order. But I suspect that they have been discontinued. I wonder if the fancy German-made brassware that I remember installing makes them uncompetitive on price. Also I see Merriott seem to supply the contract market (are a sub-brand of Purmo) and not avail. online either. Sounds interesting, do you have a link or even just a name? Will dig out the old receipts if I still have them. IIRC I got a good deal from some online intermediary that split their discount but it was actually Wolsely that shipped them direct now you mention the name. Have also found vogelundnoot but they look very pricey. .

Have posted this as a query on Victron discussion board and immediately got confirmation from two acknowledged experts there that - as I suspected - they do have cell balancing in the BMS.

A lot more choice with R32 but you will miss out on the higher flow temps and greater CoP with R290. Maybe they do not matter, or are not as important as the location.

As said upthread I do not believe this is what Pylontech do. There are very many Victron inverter installations using PT batteries and I have not seen anyone suggest/agree with this on the Victron forum, even on discussions about charging and balancing. The only major difference is that PT use 15-cell stacks rather than the 16-cell packs favoured by other mfrs so all the voltage parameters are set differently. What is the evidence for your assertion there is no proper balancing @Nickfromwales?

i have a radio teleswitch too. There was a discussion on another thread and it was pointed out that it would now be easy to fit a meter with a clock that would be sufficienty accurate over its whole life (?20 years between renewals) for this to be a non-issue. I don't know why they are not going down that route except maybe it's to move ppl to smart meters by stealth. Can't get good enough reception here for a smart meter so I don't know what their fallback plan is.

1. Some years ago I installed two big additional rads which have F&R tappings at the bottom centre. They claimed to have better output as the water went up the front panel and back down the rear so the heat into the room was more and into the wall was less. I would like to fit some more but I can't seem to find them listed any more, AFAIR they were made by Stelrad, any clues or equivalents? 2. Can you still get traditional panel rads without end panels and top grilles rather than "compacts"? I would like to get a couple to match existing. 3. An HP installer has suggested fitting "Centre Brand" rads, can't contact him today, does he mean "CenterRad" brand do we think? They seem expensive for what they are.

Have had my heat pump application failed validation for technicalities re the maps and plans. So I guess the simple way out is to pay for them to be produced professionally, has anyone got any experience of online mapping services e.g. these people?

Takes some ingenuity. Did a bit of playing around last night with a sample file as I was worried about preserving the scaling which LA seems to think v important. Can take their sample pdf from the above link, open with IrfanView, convert to bmp, edit with Paint, save as bmp, and convert back to pdf with IV. Resulting image is indistinguishable except where edited and to exactly the same scale, phew!

Here you are (from Vaillant brochure), not quite to scale, their units are 1100mm wide:

I have 3 modules (10.65 kWh) of Pylontech Force L2 and am quite happy with them. They have balancing in the BMS and the difference between min and max voltage is typically 30 mV or less. I think you will need a lot of storage if you plan on driving the HP with it, ours is not sufficient by a long way. Another 10kWh would give about 30kWh of heat during the day, from memory the payback time using it for off-peak time shifting is about 6 years. And you would need a lot of PV to keep it charged. We have a Victron 5k Multiplus II GX inverter/charger, this is rated at 4kW continuous which is enough for all domestic loads inc cooking, but IMO with an HP you would need their 8k unit.

Post spec on here, I might perhaps be interested myself if @HughF isn't. Also try this forum and diynot.

How is yr planning application going @JamesPa? I have heard today mine is not valid for various technical reasons to do with the maps and plans. Like a missing N arrow on one plan (of several) fgs. Even though I believe the additional info required would not meet the following test from the LA's own web site. "The statutory tests are as follows: reasonable having regard, in particular, to the nature and scale of the proposed development; and about a matter which it is reasonable to think will be a material consideration in the determination of the application." But they give themselves 8 weeks to respond to complaints of that nature so it is not a useful way forward, and Installer A confirms they are very picky and have caused him grief in the past So I guess the simple way out is to pay for them to be produced professionally, has anyone got any experience of online mapping services e.g. these people?

Yes in the abstract I agree, you can then achieve whatever surface area you want. But as posted elsethread, in my situation I am concerned about corrosion from the rainwater, even with treatment. Let us know what PHE you fit and how you get on. Do we infer you are close to installing your HP now, I have lost track? I have just applied for full P/P, no idea if I will get it in time to install before this winter, or whether I will still want to. Might however fit my own rad upgrades over the summer, there are some that are undersized even for the boiler so the effort will not be wasted.

Just to round this topic out, I have tried to press Vaillant's tech people about fitting a secondary circulating pump and this is what I received today. Perhaps not surprisingly they do not like to think out of their comfort zone: <I have looked around but cannot find a definitive answer on the coil size for that [OSO 210l] cylinder. The rule of thumb for sizing a coil surface area for a heat pump is 'for every 4kw of heat you need 1m2 of surface area'. This would indicate a 12kw unit would need a 3m2 surface area coil within the cylinder. For the same cylinder to be used and the water recirculated we would be unable to comment on how this would effect the running of the unit when in DHW mode. The unit will be looking for a minimum of 5k delta T when in DHW mode and may cause reduced DHW efficiency or may even go to fault if this is not achieved.>

Going back to the thread title, has anyone got more information about Phnix Greentherm R290 units, their "exclusive UK agents", performance, reliability or pricing? In short, are they to be taken as a serious player?

Thanks, good question @dpmiller. No coil proposed. Yes I could do the same as you and have a cyl with an HP size coil. Is your tank then just an inert TS or does the water in the body go somewhere? If not I think I would want a secondary pump to stir the tank for the reason you outline. Though it could all be unpressurised, so eliminating the G3 kit. But I would prefer to buy another 10l of glycol than install yet another pump. Site is on S coast so -10C protection is probably overkill, the HP has its own FP so we are talking about grid outages really and if all else fails I have a 10kWh battery too. Main concern is if we are in the Canaries at the time. It started as a thought experiment to make use of the existing tank if the installers replace it. But as you will have seen we don't now think it can be got out in one piece, however the cost of upsizing their proposed 100l buffer to 200l instead is not great. You will see from the diag that when charging, the flow through the tank is from top to bottom, and when discharging the opposite. But at a min flow for the HP of something like 20l/min a 200l tank will turn over in 10 mins or less anyway, so several times during the charging process. If the HP maintains a constant delta T across itself then effectively the whole body of water will heat slowly without stratification, that is my hope. On discharge much the same in reverse with the rads acting as a heat sink.

Maybe a bit on the high side. I have been quoted £12k8 and £13k7 all in for Stiebel-Eltron ACS 25 or Vaillant 12k, which are substantially more powerful. Both after deducting £5k BUS grant and including 7 and 10 new rads respectively.

Yes that is where we started. Does anyone have any thoughts about the proposed circuit, that is what I was hoping for? @Marvin yes my proposal does allow for the water to circulate through the bypass valve and back through the TS under all circumstances so defrosting is catered for. Neither of us sleep well in a heated bedroom so turning the heating on before the end of cheap rate (0700) is not what we want to do, the time-shifting is part of the scheme. Ditto the evening burst, it is always peak rate then and no PV. Installer A says he cannot get the HW tank out and would decommission it in situ. It sits on a shelf in a void above the airing cupboard and the top is 120 mm below the rafters. It cannot go up, down or sideways so we think he is probably right and that the whole landing wall was put up after the tank went in. He proposes to fit a new HW cylinder and a 100l buffer in the utility room which will take up more space than the oil boiler the HP replaces. Which is why I am trying to persuade him to leave the tank as is and fit the secondary pump instead as per the top right corner of my diagram. The marginal cost of the TS would then be the difference between his 100l buffer and a 200l TS, plus 2 x 3-port valves, not £2000 (I already have a spare pump and the 2-channel timer). His proposal is silent on frost protection. I would prefer glycol, since the water will need additives anyway and dumping it in the middle of winter would take some sorting out. 100l extra fluid would mean only 10-20l more glycol. OTOH Installer B thinks he can put in a new tank where the old one is. If he can get the new one in then he can surely get the old one out without sawing it up, complete with its G3 valve group. So in that case we can use it as a pressurised TS at negative cost as he would not then need the 100l buffer he is proposing, and also mean only one large vessel in the utility room so take up less space. His proposal does include antifreeze valves. Installer C also quotes for fitting antifreeze valves and expressly mentions inhibitor. His budgetary quote was 1.5 times the others and includes new pipework throughout the house so we are not going with that.

1. As discussed elsethread here is the proposed diagram for a Thermal Store in conjunction with an Arotherm Plus. I don't know if there is an approved Vaillant way of doing this (as distinct from a Buffer) but I haven't been able to find one. Perhaps there is more in the documentation for installers. The idea is to charge up the thermal store using off-peak electricity in the small hours and free PV in the daytime, and use it to heat the rads in the master bedroom for an hour morning and evening when electricity is much more expensive. Calcs show heating a 210l cyl by 12 deg will store 3kWh which is enough to heat the bedroom, and this could save about 360kWh of electricity per year. Referring to the diagram below: Normally the two 3-port valves A and B are in the straight-through (black) position and the rad zone is controlled by valve R1 as per the normal arrangement in the Vaillant schematics. To charge up the TS the 3rd party programmer sends a demand signal to the VR71 where it is programmed as Zone 3, this activates Valve A and the flow is diverted into the store. To discharge the TS through the radiator circuit the programmer actuates Valve B and the pump next to it directly to feed the rads. The HP can be on or off during this. In normal operation all the return flows (including the auto bypass) would pass through the lower part of the tank so it would also act as a volumiser. 2. Recirculation of DHW on the secondary side You might recall I have done some tests which indicate that the heat transfer is likely to be increased by a factor of 2 by circulating the bulk water in the DHW using a small bronze pump e.g. https://www.pumpsukltd.com/lowara-ecocirc-pro-15-1-65b-bronze-circulator-1-230v.html. This will mean a heat transfer rate of about 6 kW; the Arotherm Plus can turn down to 6kW so it will not need to cycle on and off. This would be much easier to implement than a replacement cylinder or fitting a heat exchanger. Getting the existing cylinder out from above the airing cupboard would require a lot of structural work. We can live with the longer reheat time as the tank will be heated during the afternoon and in the small hours when we are not using the hot water anyway. If we have a lot of visitors there is also the 3kW immersion which we can run off the PV diverter. Would appreciate all sensible comments!

Yes, it is long and thin, originally two barns. The upstairs layout is Master Bedroom, Guest Bedroom/Study1, Boxroom/Study2, Guest Bedroom 2 all in a row, with 6 wireless TRVs. By default if it is nice outside and no-one has come to stay then only the MB gets turned on at all. We have seriously considered in very cold weather living in the kitchen/dining room where the AGA is, and not heating the other end of the house at all. The AGA flue runs up inside the MB and also the boxing round it feeds into the MVHR system which helps further. Downstairs there are four zones of UFH each with their own hardwired thermostat, plus the two rads I have added in the living room with their own wireless TRVs. If sunny there is quite a lot of solar gain so it does not need much heat until after dark. Some simplification of controls is perhaps feasible. Installer C expressly quoted for separate stats upstairs and downstairs but we defo need something finer grained than that. As explained above zoning into the E barn and W barn would make at least as much sense. The other proposals were altogether very vague about controls. I get all the stuff about long and low - the AGA, UFH and stone walls provide a natural setback level everywhere and then with the controllability we now have we can spot heat the rooms only as and when we come to use them. OK this is a boiler replacement philosophy, which is where I began.

What counts as a "new" heating system for the purposes of Part L? If you are doing a like-for-like gas boiler replacement then surely you are not expected to recalculate the emitters for 55C and upgrade all the rads at the same time. Why should changing the heat source to an HP affect this? Does that somehow make it more "new"?

This. Describes my situation exactly. Honeywell Evohome took a long time to get working (because there are no diagnostics to show which (defective) wireless TRV is calling for heat) but I am not going to scrap it now and install a new Vaillant ambiSense controller and new valves throughout at £81-28 a pop. Just tried to ring Installer A at 1205 on a working day. Biggish firm but just rings out, can hear it divert (twice), no recorded message or answering m/c or anything. BTW1 I see the Heat Pump Installer Network has been set up specifically to train everyday plumbers as HP installers but looks in the very early stages ATM. Investors include EDF BTW2 I see also that Freedom Heat Pumps are now owned by Certas (the oil distributor who were forced to divest themselves of BoilerJuice after an anti-competitive outcry) - notice a pattern here? BTW3 I think I have worked out why my cyl has 15mm F&R, the piping is so short it might have starved the rad circuit if done in 22. Is S-plan so both can be on at once. A turn-down valve might have been more useful (and cheaper than all the 22-15 reducers).

Interesting post on an earlier exhibition in Frankfurt by Graham Hendra, some further comments much in line with the thoughts of @JamesPa here. All of which inclines me to wait until some more of these R290 machines hit the market. Will still require a change of attitude on the part of MCS installer hierarchy though to design for flow temps higher than 45C. Part L allows 55C for retrofit but even that does not really make best advantage of the higher temps achievable IMO.