Benpointer

You say that now! We said similar 12 years ago having completed ours but guess what, we're just getting market valuations to sell and do another project. This time we'll get it right!

Neff induction hob in black granite island worktop. installed 13 years ago. Works for us. The granite was CNC-cut based on a CAD provided by Neff.

Problem solved! Somewhat embarrassingly, it's turned out to be a failed zone valve head on the UFH circuit - the microswitch not sending back to the FTC2 to trigger the ASHP pumps. New head fitted today - pumps now working! Thanks all!

The flow & return pumps definitely do work - they work if HW is being demanded. It just seems that the controller is not triggering the flow & return pump relay when UFH is requested. Hence my thought of putting the flow & return pumps on the same electrical circuit as the UFH pump. (That would mean the system would not work for DHW - but we never use it for that anyway.)

Regarding the flow and return pump. This is from the Ecodan Design, Installation & Servicing Instructions manual: "Each of the Ecodan® models require sufficient primary flow rate for adequate operation. Due to the large resistances caused by the plate heat exchanger in the Ecodan®, two domestic circulating pumps in series to produce the required flow rates. These pumps must be set to the same speed or damage to the system may occur." And this diagram:

I'd just like to reiterate (paraphrase) my original question - could put the flow & return pumps on the same circuit as the UFH pump? That would mean every time the UFH is demanding the ASHP flow & return will run. (It won't work for HW but we don't use that anyway.)

Yes. We can heat the HW and the ASHP flow and return pumps F&G switch on when HW is on demand. But no, we don't heat HW from the ASHP because (sigh) there is a long-standing issue where the controller errors every few days when trying to heat HW. We had someone look at this a few years ago and the upshot was, quote "It's a known issue with the FTC2, which is out of warranty and Mitsubishi won't fix, so you could either pay for a new controller or, since you have an immersion heater, use that". Which is what we have done ever since. It's not so bad as it sounds as we have solar HW too but still we are spending money on the immersion heater.

Q: Has it ever worked? Well, it's hard to be sure (because we have never actually checked that pumps F&G were spinning in the past) but the house has always able to maintain a good temperature even through periods of severe cold as in 2010, 2013 and 2018 (the 'beast from the east'). So I suspect it was working ok up until recently. Q: Why is there both a flow and return pump? No idea, I suspect the original plumber didn't really know what he was doing. I also suspect it's overkill but... that's not the issue at the moment - neither of the flow or return pumps are switching on when the UFH is on demand. (Edit: In fairness to the plumber, the Ecodan installation manual shows both a flow and return pump.) Re checking the wiring and controls: The pumps come on when the HW is on demand, so I think the wiring is ok. The FTC2 is probably at fault but Mitsubishi want £240 just for someone to come and have a look (!)

We have a fault with our Ecodan 85 FTC2 controller whereby the controller does not switch on the Flow and Return pumps (F&G on the schematic below) when the UFH is demanding. It does switch those pumps on when HW is on demand. Despite this, the UFH pump (E - which does power up as it's controlled directly from the UFH circuit, not the FTC2) seems to draw enough water through the ASHP to provide heating to the floors on most days. It seems to do this in short (5-10 min) cycles with the flow temperature quickly rising to meet the flow target temp, the ASHP cutting out, the flow temp dropping and the ASHP cutting in again. However, on cold days such as those experienced before Christmas, the heating is not reaching the room stat targets. I have a support query lodged with Mitsubishi for this but in case they fail to come back or simply say our system needs replacing, I have the following question for this forum: Is it safe to run the Edodan flow and return pumps even when the ASHP is not operating? (i.e. have the water circulating through the ASHP when the compressor is not running. If so, I could run these pumps off the same circuit as the UFH pump (E) because we don't use the ASHP to heat our hot water at all.

For what it's worth, ee did much the same to our 1960s bungalow: 100mm brick, 60mm cavity filled with blown polystyrene beads, 100mm brick, 2 layers of Kingspan K5 50mm on the outside with staggered joins, rendered over with K-Rend. We put fresh 12mm plasterboard on the inside in preference to re-skimming the rather flaky old plaster. No VCL fitted. We have had no damp problems at all. We do have whole house MVHR which helps prevent damp I believe. I will probably take a similar approach on our next project, maybe with even more insulation on the outside, depending on the heat loss calcs.

We put in a 3500l rainwater harvesting system when we did our house 12 years ago, for WC flushing, running the washing m/c and garden watering. I wouldn't do it again. Issues include: The water is of course unchlorinated, so you get brown toilet u-bends after a while (and the insides of the cisterns go black with mould, not that you see those of course). The washing never felt entirely 'clean'. We switched the toilets and washing m/c to mains after a few years for the above reasons. The tank ran out regularly each summer and the automatic top-up seemed to waste quite a bit of water down the tank overflow as it was delivered to the tank via the drainpipes and thus the leaf filter. The pump failed after 8 years and cost about £300 to repair (versus £700 to replace) The electric controller failed last year, so now we just switch the pump on manually when we want to water the garden. And it still runs out as soon as we have a dry period (ok we have a big garden and a lot of watering. So in short: nice idea but really not worth it. It's certainly never paid for itself. Sorry to be negative.

Very limited choice round here (north Dorset) but yes, I take your point. If anyone can recommend a good plumbing firm that knows something about underfloor heating and ASHPs near Shaftesbury, that would be great but it seems the vast majority of firms don't have experience of ASHPs and UFH.

Doh! Yes should've done that! 🤦‍♂️ Anyway, there wasn't much above 55C in the top of the tank; I duly dumped it. And hey presto the ASHP ran consistently at 3.5 kW draw for 20 mins without a problem heating the water. I did notice some build up of frost on the back of the ASHP but to be expected, I guess. Seem to prove the issue is not with the ASHP itself. So... On further investigation there is a mixer valve on the UFH heating circuit (photo below), presumably to ensure the flow to the floor is not too hot. It was set to MIN. (When? Did I do that in the summer to 'save money' - I don't remember doing so). I have now set mixer valve to MAX and the ASHP has been running uninterrupted since(!), showing 41C target and 41C actual flow temp. So that's progress. I'm not totally out of the woods yet though as the ASHP is still only drawing about 1.0 kW. My assumption at this point is that there is a flow issue with the UFH that prevents the 41C water getting to the floors at a sufficiently high rate, thus the ASHP is not having to work very hard to keep the UFH water at 41C. Not quite sure the where to go next. There's a Boiler Buddy which has never been cleaned to my knowledge so that may be worth looking at (albeit, it's on the ASHP circuit so would affect both UFH an DHW if that was the issue). There's a dedicated pump for the UFH circuits but if that had failed, I assume we'd have no heating at all. The lad the plumbing firm sent round was not much use btw - scratched his head then called his boss, who suggested the ASHP might need re-gassing (why?) Photo of the UFH mixer valve, now set to MAX:

I am going to try to see if I can get the ASHP to run without interruption in Hot Water mode, rather than UFH, in an attempt to rule out blockages in the UFH circuit. Normally we don't use the ASHP for HW because, reasons, but it is connected for HW. (We use solar HW and an immersion for HW). Just need to persuade Mrs. P. it's ok to dump 100l of 65C water to get the thermostat to trigger ASHP HW heating (!)

Well I think so but I am not sure how I would tell for sure? There appear to be two circulation pumps, one on the out and one on the return. I do have a plumber coming out to look at the issue tomorrow but he is not an ASHP expert - I am hoping he will either give the UFH a clean bill of health or spot and resolve the issue. Again, I am not sure how to tell for certain. The side and back look frosty for sure but not, as far as I can tell, full of ice. Here are a couple of photos: (Thanks for the replies btw!)

PS, just to say Emporia shows the Ecodan is drawing an average of about 1.1kWh each hour, so our COP adjusted 8.5kW ASHP is more like a 3kW heat pump at the moment, which is clearly not enough to keep even our well-insulated bungalow (c180m2) warm.

Hi all, We've just got back from a weekend away to find our ASHP-underfloor-heated house rather cold (17C versus thermostat settings of 20-23C in various rooms). Obviously it's cold outside (-0.9C at present) but we've never had this before and our system has been in 12 years. It's a Mitsubishi Ecodan 8.5kW pump. Both the ASHP and the underfloor heating appear to be on. The UFH is showing demand from all zones as you would expect. The ASHP is in Heating Eco mode and has the target water temp set to 43C. Checking the power use of the ASHP with my Emporia monitoring I see that it is cycling between no power and full power (c.2.6kW) every 10 minutes or so, as follows: Here's a cycle in second intervals: Over the same 10 minute cycle the actual water temperature rises from 27C to 46C and then falls rapidly back again to 26-27C once the ASPH stops. It feels like the problem may lie with the UFH circulation rather than the ASHP. As I say, we had the system for 12 years without issue and we've been able to keep the house nice and warm through previous snaps. If anyone has got any ideas about what the issue is, I'd be grateful. Thanks

Just thought I'd mention that Earthwise got back to my question about whether there was any way they could recommend to combine a Solic 200 and a timer, with the following fulsome reply: "Hi, The SOLiC is designed to mounted on its own dedicated circuit so fitting a timer is difficult. Thanks Iain CM McRitchie, FCCA Director" So that'll be a 'no' then.

Er... Sorry to butt in on this one but in our FIT scheme at least we get an export payment for 50% of what we generate, regardless of how much we actually export. That is because the company paying our FIT (Energy Warehouse) has no way of knowing how much we actually export - there is no meter for that. So an assumption is made that we export 50%. We don't have a battery - I've looked but I still think the pay-back is too long, we don't plan to be in this house for many years. But if we did install a battery, we'd still get an export payment for 50% of what we generate even if never exported anything. Edit: Apols @FerdinandI see you have made the point about 50% assumed export where you don't have an export meter.

Thanks for the suggestions everyone. I have contacted Earthwise to see what they suggest. Don't know why I didn't think of that before. As has been suggested the Boost function would be fine if you could have it happen at say 19:00 every day. (Maybe I should build a little bot to press the button each evening 😁) The changeover relay/contactor solution sounds like it ought to work but I would need to get my head around it to be totally confident. It will be interesting to see if Earthwise recommend that. Thanks once again for all the ideas!

Many thanks for the reply. Yes, it would be nice to fix the ASHP issue but... it's an early Ecodan 85 with an FTC2 controller, bought and installed very cheaply 12years ago, without a warranty. Several (Mitsubishi companies) people have been to look at it but none could solve the problem. The latest, this year, said our best option is to live with it until the ASHP fails when it will probably be cheaper to put a completely new unit in rather than trying to fix it. Regarding a timer. We have used the LAP timer (not the most reliable tbh, failed after a couple of years). We do have a very good digital timer on the immersion heater now but the question is: how can we run a timer and the PV diverter in parallel, so that the PV diverter heats the HW during the day when we have excess PV and the timer comes in in the evening if there has not been been enough PV to take the HW up to the IH cut-off temperature?

The Earthwise Solic 200 looks like a good piece of kit for half the price of its competitors but doesn't seem to include a timer to force the immersion heater on if the tank has not been heated up during the day by diverted PV. Currently, we have to use an immersion heater to heat our hot water in the winter because our old ASHP controller has always locked out when trying to heat HW. (Although we do have solar HW too which works well in the summer.) So ideally, I'd like the immersion heater to use diverted excess PV during the day and then come on for a couple of hours during the early evening (from the grid) to heat the HW if it is not up to temperature. Anyone know a way I could combine a time and the Solic 200? Thanks!

Lol yes, maybe that's right. As least we will be able to drink the contents of our wine cellar as we go. 😉

Sorry to post this but I'm having some dark thoughts... I have 4kW of PV panels, no battery. I appreciate I cannot use the power generated by the PV during a grid power cut. But if the worst happened with Russia and the grid failed permanently, yet here in rural Dorset we were still alive, is there anyway I could completely disconnect from the (non-working) grid and configure the panels and inverter to make use of that PV generation during the day?

Haha thanks - I think I'll save that for the day Emporia want to start charging a subscription!