Benjseb

A quick update Ow our heating has been running for the last 5 weeks 24/7 (ASHP) at 18-19c we’ve noticed not a huge difference, maybe high 70s to low 70s weve started running a dehumidifier downstairs that’s under specced but has kept the humidity down to 60-65% Im thinking that adding a PIV unit (or two, big house) may get that down to mid fifties to make it less of an issue? We already have 4xDMEV trickle extractors so can work in conjunction with them. if so, am I right in thinking that’s Best to situate the PIV inlet in the dryer end of the house, so it pushes the damper air out around the source rooms, rather than pushing it into the dryer rooms? Also seen our trickle vents are just two 8mm holes drilled in the frame of each window! Can’t see them doing much as the resistance will stop much flow. Might have to drill some more holes out Ben

Our HP (Misubishi) doesn’t need a buffer tank but we went with one anyway as we wanted to be able to a) heat with an immersion if the HP had issues and b) divert some solar to it if the DHW tank was already warm as Joe said ours works the same, stays at 40c then can supply water instantly when zones open. I think our HP would do that anyway without a larger buffer tho so it may slightly increase running costs due to the buffer tank losses.

Following on from this and my post about actuators yesterday I’m feeling that running our UFH as one big zone may be better too its only 2 zones which are adjacent rooms. One is a kitchen so perhaps I’ll dial down the flow rate a little as it gets heated by cooking that then eliminates the actuators delays without any cost and keeps the whole thing simple

Yes all clear at £200 to replace the actuators though I am wondering if it’s worth the expense. Our loops are all about the same length so not sure if we will get that much benefit

Thanks @JSHarristhats clearer now i will give this a go with 2 of our 4 actuators and see how they compare it certainly appeals that they do t take 10 mins to react, and the balancing is a bonus on top.

Yes I’m unclear. surely the only part of the system that can blend down the temp is the mixing valve as it has both flow and return inputs. the actuators are simply flow rate of the return feed. Sealed loop so can only co tell flow, not temp? i guess it controls delta T by adjusting the flow rate

Am I right I’m thinking it’ll just allow the HP flow temp through tho - say 40c - even at a slower rate perhaps, so if we’re not mixing it down it won’t be as efficient?

Thanks @JSHarris did you notice much advantage after doing this? i have noticed that the pump fires up a few minutes before the actuators open which isn’t great so that may help. Does the auto balancing help? Ben

I think ours says the same. So not really suitable for heat pumps then!

This is interesting! As our current actuators are controlled by the stats what happens if the demand for heat is satisfied, how do you close the zone off? Do they work if it’s not a thick slab? Ours is A retrofit system under tiles. The current actuators are very slow though but currently each zone only comes on for a few mins per hour as it much heat is needed

I have an ASHP which runs UFH and rads the flow temp from the heat pump is usually 38-45c Wr can run the UFH at a lower temp than this. However, the valve seems a bit... shit. if I set to 35c I only get flow temp of 25. If I set to 45, it gets to about 30-35. However that 10c difference changes depending upon the heat pump flow temp. The instructions for the valve state that for it to work correctly the incoming hot flow needs to be approx 15c higher than the desired temp. is that normal? Or have a just got a cheap mixing valve? ideally I’d like the UFH to stay at about 35 as it’s only really the rads that need a higher temp when it’s cold.

Yep they are upsized. It still take a lot longer to warm up though than the UFH which is probably 4x bigger than needed so just a case of one working more effectively than the other really. They should all still kick out the heat needed.

First coldish day today as the outside temp dipped to 3c this morning and about 5c this eve Everything is toasty at 19c. we can really tell the difference between the lounge which has radiators and the other rooms with UFH. They don’t seem to call for much heat at all as the tiles just gently give off some heat after turning off. The lounge takes a lot longer to warm up. Might have to do some extra draughproofing and add some thick curtains so we can keep the flow temp low But it’s still within design specs It’s currently running at 42c this eve which I’m happy for as we specced it to run at 50c at -2.5c so about right.

Quick question... Is it usual on these systems to have the heat pump keeping the flow temp to our set temperature, 24/7, even when all the heating zones aren't calling for heat? Seems the room stats link to the zone valve/pump for that zone, but don't interface with the Ecodan in any way. So if our rooms are all at 20c, with the stats set to 18c, even if no heat is called for all day, the ecodan is still spinning up to keep the flow temp to 40c for instance. Understandably this water shouldn't change much with no heating load, but seems a waste to be continually circulating the water from the heat pump to the buffer tank when no demand?

And we're done, all installed and working We've not had an oil boiler since May so glad it's in! use in time too by the looks of the news with the Saudi oil strikes. Great that we're fully pumped now and not on the horrible gravity fed system we had - so many air blockages previously! Now to try out the underfloor heating!

Yes it’s primarily due to it being a courtyard with walls all around and neighbours bedroom nearby so didn’t want the sound bouncing off the walls at night. I know they are quite quiet now but when amplified and reflected we didn’t want to risk annoying people! it would also have needed a run of pipe probably 4-5m anyway compared to 8-9 now.

No not really. The house is quite picturesque from the front and it would be right near the front door. At the back it’s a north facing courtyard so not ideal due to sound and cooler temps. We we didn’t really want the heat pump smack bang in the middle of the house layout so it’s gone where the oil tank was. Using pre-insulated buried pipes so hopefully heat loss will be minimal.

I am! We’re getting there. Tanks and water filters (chlorine/etc) in today.

The week has finally arrived to have our old oil boiler and a huge 500L water tank ripped out and a new AHSP installed Can't wait - especially as we now have no hot water until it's connected! So far the oil tank has been removed, we've dug a big trench to lay the pre-insulated pipe into, and the old Whitebird 120/150 oil boiler is going on eBay! Hopefully today the cylinder will be in so we can have a warm shower, then everything else will get connected up and commissioned tomorrow

Any further suggestions based upon the extra info above? Thanks all.

Thanks guys So to give a bit more info, the house is 'long and thin' - most rooms are the depth of the house, so have two external walls, both north and south facing. On the ends the rooms have three external walls. 2 storey, The kitchen is an end room, so West/South/North facing 42sqm. 60W/m2 heat loss Stone built. Brick inner leaf. Insulated internally. There are some fairly large half-glazed doors on the north wall, plus a small double glazed window and small door on the south facing wall. We're not interested in insulating it further, as it would be too disruptive, and it's not "cold" by any stretch, it just sits at say 17c most of the year unheated so feels like a little extra solar gain and light would make a difference, like it does in the other rooms. Ben

We have a largish kitchen (50sqm) which stays quite cool all year round due to lots of stone and insulation its lovely in the summer and rarely goes about 20c. It’s south, north and west facing! However in the shoulder months we tend to have to extend the heating to take the edge off as there’s only small windows. whereas other more glazed rooms are warmer. We were here considering knocking a small window/wall into a bifold door. This would be south facing so give some decent solar gain hopefully. How can we balance this so it works well and doesn’t lead to a cold room in winter. I’m thinking triple glazed, is that enough, I’m not really sure how they perform as never had bifolds. Thanks ben

I can’t see a breakdown on costs Our house is 250sqm but it’s old stone build. EPC C/D (depending upon which one you read!) Our heat loss came back at 13kW. There’s no way you should estimate this. Do it properly our 14kW Mitsubishi Ecodan plus 120l buffet plus 300l DHW tank was £10k ish plus vat. That’s with cloud monitoring and 5yr warranty. Also, I’d go for a biggish water tank then you can keep it at a lower temp (say 47c) which is more efficient to heat than a smaller tank at 55

Sept 9th the install starts. If they can get the old 500l hot water tank out of the room! ? no PV yet but we’re converting a garage into a holiday let later this year and it’s got a decent East/West roof so planning on adding some to that. Weve asked for a buffer tank with an immersion so we can divert to DHW or buffer tank if we’re lucky enough to have excess at the right time of year. I think we can either fit a 6kw system on single phase or 9kw on 3 phase. But trying to avoid using 3 phase as it will mean we get to consume less of the electric we generate.

We don’t actually have any condensation issues at all, not even in the bedroom if the windows are closed overnight the thinking behind PIV was that our humidity is over 70% currently (usually about 60-65%) and I just want to ensure the air is as fresh as possible for health reasons. With an old stone house there’s always going to be moisture in the air so it’s more of a way of proactively managing this I guess. But as usual it’s a balancing game as don’t want to be pushing all the warm air out.