Bramco

@Great_scot_selfbuild - thanks, I'll tell the builders next time I see them. Those saris rooflights look exactly the same as the Roofmaker rooflights we used -> https://roof-maker.co.uk/products/hinged-opening-flat-rooflights/. Think they do these in a variety of glass types/u values. Ours are triple glazed as in the link and work very well. On the blinds aspect, ours are in the living space and bathrooms and on a landing, so we're not worried about having blinds. Wonder if @JamesP has blinds? If you're thinking blinds to cut out solar gain, then maybe it would be enough to simply open the roof lights to dissipate the heat. Works for us. The cladding is Greencoat (afaik) specced for longevity. I can check the exact spec if you need that. Here's a link to the architect's web site with more photos -> https://lhc.net/projects/ashcroft-creating-a-low-energy-family-home/

@Great_scot_selfbuild We didn't use Velux - hate the stand up edges. We did use the Roofmaker skylights that it looks like you have used on your garage. Ours are flush with the corrugated roof. Essentially you have to leave a large gap at the bottom of the roof light, create a slight slope and then mold a water resistant membrane across that and onto the top edge of the roof below the roof-light. Ill have to check with the builder and architect what we eventually used - was 3 years ago. EDIT: checked and we used -> https://www.deks.co.uk/fast-flash See photo - I have the architects drawings for this if you DM me. PS What's the reason for using Velux rather than the Roofmaker roof-lights?

Not sure why a brick or block skin would be seen to be giving more surety - it's only a skin and the fabric is timber frame. Just goes to show how thick industries like insurance etc. can be at times... I wonder how everyone in Scotland copes? What with timber frame being much more prevalent there - afaik. Have you tried Scottish mortgage companies? Also, isn't there a timber frame manufacturers association? It may be worth contacting them. Or just going round to a local building site - there's a lot of timber frame going up at the moment - how are they advising their clients on mortgages? Or take out a buy-to-let mortgage on the property - and get a postbox address for correspondence.... 😉 🙂

Yes it's essential in a house which is nearly airtight - and if you are self building and don't intend to make things nearly airtight, then you've got to be daft because all of your heat will disappear into the environment through the draughts. But you need either a good builder, or a lot of patience to get the airtightness. And a lot of attention to details - window frames should not have vents etc. Air quality internally should be much better as well as the air entering the house has been filtered.

Would be interesting to see the last charts by Battery kW, then cost per SAP point. In terms of our thinking, 5kW of battery wasn't going to achieve a lot but then deciding whether to go 10 or 15 was. Same goes, I guess, for PV. The costs of installing 2kWp would be crazy and that shows I think in the earlier sheets.

Sizing the inverter depends on few things - what is the maximum PV output, what is the maximum draw from the house etc. Given you'll almost never get the maximum PV output and the estimated output is 6kW, you'd be OK with a 6kW inverter. On the house side, the biggest draw from appliances is about 3kW, so you could draw 6kW from the batteries without pulling anything from the grid. But if you want a fast EV charger, they would pull more but then it would depend on what the batteries can deliver. Don't know what Sigenergy can do but it will be on the spec. If you plan to do EV charging from off peak, at night, then this might not matter. Personally I'd put more battery capacity in rather than a larger inverter. If you are on O Go Int, then you can dump almost everything in the batteries in the evening at 15p before the cheap rate starts and then refill them at 7p. It's a bit of a no brainer. So the larger your batteries, the more you gain. Having said that, we are single phase, so I don't know how this would work with 3 phase.

The way we use the thermostats is really only for the scheduling and as temp limiters. The thermostat schedules (3) are set to come on just after the start of the cheap rate and are set in one hour chunks. First hour is at 24C then we drop gradually hour by hour down and the last hours are at 22C. This ensures that the thermostats don't do their stop start business, so the ASHP is on constantly until the target temperature is reached. Seems to work for us. If we dropped the thermostats and went over to WC with a setpoint, then we'd have to find some other way of scheduling the night time batch charging of the slab. So we'll stick with the thermostats.

So the hot side of the house can't take any heat but the cold side can - so any flow through the hot side comes back still hot whereas the flow through the cool side comes back cooler. Trying to get my head round how this would work for those of us with insulated slabs with UFH that batch charge the slab at night on cheap rate lekky. I guess the same would happen - loops in cooler parts of the slab would suck up more heat than those in warmer parts. So the only setting is the setpoint set on the ASHP. What is yours set to against the temperature you are trying to achieve in the house?

You obviously live alone... Where thermostats have a display, isn't that what the display is?

You're making the assumption that someone in the house (you know who I'm talking about) can guess the temperature without looking at the app - ain't gonna happen..... 😄

Could do but... In our setup, we only need to run the ASHP at night to batch charge the insulated slab. When it is cold, all the rooms need the full 6 hours or so. When it is less cold, the thermostats will cut off the flow when the set temperature is reached. So for the downstairs bedroom it cuts the flow off earlier than the other two living area zones - the set point is lower. I do set the thermostats in 1 hour intervals starting a couple of degrees higher than needed and decreasing the setpoint every hour. This makes sure that the thermostats don't dick around with the ASHP by tuning it on and off at short intervals. Again this seems to work fine.

Thanks for the suggestions guys - I'd put solving this on the back burner as we had a workable if slightly more expensive solution - think I probably need to give this a bit higher priority on the to-do list.... The UFH buffer tank is a smaller Newark tank (140l) - earlier when I contacted them, they said they put either one or two coils to get the 3m2 surface arear depending on the size of the cylinder. So I guess they always put two in on one that is 140l. Our 300l DHW tank has only one.

@Wil thanks and I know how to do the change manually - there's a few owners on another thread trying to work out how to do it automatically. I wonder if we maybe haven't the same unit - mine is wired using pairs on a cat5 cable, not through an rj45 connector. Do you have the pinout for your connector.

Thanks

I know I do.... 🙂 Long discussion here -> https://community.openenergymonitor.org/t/water-hammer-noises-and-heat-pump/26263 And you've been short changed - mine has a couple of those. 😄 and they haven't worked on the air trapped in the corrugations in the DHW tank.

It's been stated many times...... 😄 Sadly we have a DHW tank with an ASHP coil (3m2) BUT it's corrugated which leads to a lot of noise from air trapped in the corrugations. Manufacturer says - your problem mate. The fix is to replumb with a deareator etc to try to get rid of the air. So given we lose a bit on using the diverter rather than the ASHP, we have some way to go before it cancels out the cost of the replumbing - I'd also add a heat meter and the kit to be able to monitor the CoP, so it's not a cheap solution fix - and it may not work!

Could do that and tbh, in the summer the tank is hot to overflowing with all the solar divert. I'd just have to remember to go back to heating only before the winter. Although at ambient it wouldn't come on anyway...

@Wil @MikeSharp01 @alfaTom Looks like you all have been through the CE MCS scheme and self installed. I'm assuming that when the unit arrived, there was some detail on what connections to make between the indoor Carel user interface and the ASHP itself. I've worked out which additional connections can be used to switch between Heating and Cooling but can't work out how to turn off Hot Water. So wondered if the connection instructions you received had this info?

DI-6 works the same way as DI-4. So connecting to GND (8) sets the unit in 'Hot Water + Cooling/Heating' depending on which one is connected. Given we don't use the Hot Water modes, only Cooling or Heating, I'm going to have to find out how to switch off Hot Water....

Good question. I've redone the experiment swapping from heating to cooling and when I look in the app to set things back to heating, it shows the unit as being in cooling + DHW. So it looks as though connecting DI-4 to ground hasn't set the unit to just cooling, it's set it to cooling +DHW. Which means, I'll have to find out how to turn off DHW as we only use the unit for heating and cooling..... I'll attach another wire to the DI-6 for setting things back to heating to see what happens. Can't see anything on the schematics for DHW - although the schematics are very blurry, so it's hard to tell.

You'll have to connect DI-6 to common to put the unit back in heating mode. DI-4 and DI-6 are latches, so making the contact and breaking it doesn't return the unit to the previous mode. I'm going to build something in parallel to the thermostats which when activated will run cooling at night on the cheap rate. I'll also have a boost button for, say, 3 hours for when we need additional cooling during the day. Will also make it accessible through Google Home, so if we're away for a long time, I can turn it on remotely.

@HughF Interesting - it works as a latch. (Probably should have expected this thinking about it). So when you connect DI-4 to GND, the unit switches from heating to cooling. But when you disconnect it, it stays on cooling, so you'd have to connect DI-3 to GND to get it to switch back to heating, or do that on the controller or app. With a suitable relay, you could switch to cooling and then drop back to heating but you'd need 3 wires. Simon

@HughF thanks - there's a spare pair on the cat 5 into the house, so I'll rig that up with a switch in the house to see what it does. Simon

@HughF I'm assuming that these connections override whatever may be programmed on the internal Carel controller (and the app)? So you could leave the controller/app on Heating but have a relay make the connection between DI-common and DI-4 and the unit would switch to Cooling mode. Obvs, I'd need to also provide switched live to the 4 zones on our Heatmiser UH4 wiring centre to open the valves on the manifold and give the ASHP the boiler enable signal. In our case, we'd have to replicate the programming for when the cooling comes on which is currently in the thermostats but that's pretty easy to sort out. We normally run the ASHP at night on off peak.

Thanks @HughF Like Mike, I'd ignored that page because it was headed 3-phase unit and we've a single phase unit - next time I speak to them, I'll point this out. Simon