RobLe

I think at least one drain hole is needed to vent to outdoor air that is usually lower absolute humidity than indoor air.

I think there should be an air gap all the way around the double glazing seal(the one built into the sealed units) and that air gap should vent outside at the lowest point. It’s both to vent liquid water that gets in, and to ensure that you don’t get condensation on the dg seal that will eventually make the dg unit fail. It’s true for all dg windows as far as I know.

If you’ve got pre 2000 uPVC windows that are in good nick with internal beads, I think it’s worth replacing the U=2.7 glass units. We did this 15 years ago - our frames are 35 years old now, but with newer planitherm one glass and diy foam filled frames(make sure that water can drain). It’s a tough decision to not change the whole window for a more expensive ‘eco’ one; we could have afforded it - I just hate skipping perfectly good stuff. Plastic is a problem - throwing a window frame away doesn’t help.

That COP is so low, that I think something odd is happening, as opposed to the usual high flow temperature at the ashp. I think ostensibly it suggests an average COP of (124+38)/124 =1.3. This may or may not include the weekly immersion use. You don’t complain of a cold house; in this weather if the COP were actually that low I’m surprised the unit can actually warm the house sufficiently. Has it always been like this? Suggestions to try: I note that 124kWh elec in a cold week is not insane - can you calculate your heat loss in kW, see how it compares to an hour of the generate+consumption at the design external temperature? Fit an independent mid-certified elec meter to the ashp, and also a heat meter - more effort this, but will give a believable COP. Eg opentherm.

You can figure it out from a thermal conductivity (U value) ratios, based on a known value: Indoors, in still air, a vertical boundry air layer has a U value of 8W/m^2/degC. That is from the centre pane glass surface, to the air temperature in the middle of the room. The U value of the glass represents the heatflow per m^2/degC through the glass, based on the air temperature in the middle of the room and the outdoor air temperature. So, if you measure the values below with the same IR thermometer pointed at a bit of tape stuck on the glass etc: Tindoor = the indoor air temp Toutdoor = the outdoor air temp Tglass = indoor centre pane glass temp Uglass = 8* (Tindoor - Tglass)/(Tindoor - Toutdoor) I can generally get the answer within +/-20% of the expected value when it's cold outside. That's good enough to tell if the units are just glass, or have a coating on them.

Your walls likely don’t have CWI (cavity wall insulation); you can usually see the pattern drilled into them if it’s been done. Typically 25mm dia holes into morter, every 500mm or so over the entire wall. Suggest taking a photo of the brickwork (regular, not IR), and we can likely tell.

It’s most likely that your DG windows are U=2.7W/m2/degC, or thereabouts - that’s what you get from two panes of glass with a 16mm air gap between, as happened until around 20 years ago. It’s possible to measure the U value of a window. Now there’s a metal low emission film applied, a warm edge spacer, and ‘heavier than air’ gas inside the cavity. The obvious thing to check first is if you e had your cavity filled yet? You can generally tell from the brick pattern outside. I say this as the wall looks cold too.

While I agree you can draw over 3.6kW in a home, in practice I believe it’s sufficient for most people. We have 2+2 people here, and don’t make any attempt to limit our combined appliance useage - kettle/cooker/washing/gshp(v small) whatever. Cars charge and dhw heats at night on the cheap rate. Our 3.6kW sunsynk +15kWh Seplos batt system charges at night in the winter, and gives us 97.3% cheap rate elec useage. The most significant aspect I found for improving the cheap rate useage has been getting the CT coil noise related offset working well. pic below ignoring export:

Yes. eg a sunsynk 3.6kW Ecco, will allow 2 strings of 425V*13A max. It can charge a 16cell LiFePo4 batt at 90A while sending 3.6kW to grid. Or get an even bigger unit that is g100 certified, and get the overall grid export limited to 3.6kW.

There might be an issue with a heatpump being force fed super hot water into its heat exchangers, which a gas boiler could do. Doubt an issue in practice, but let’s say you pushed in water at 90C then the refrigerant pressure might end up above the heat exchanger design pressure. Maybe. We ran with a heatpump and a gas boiler for a year and a half, until Mrs RobL was convinced the new fangled (diy) heatpump was ok. The electrics totally switched one or the other in with a 4 way rotary switch, the water flow was magnetic filter->gas boiler->heatpump, and the heatpump flow & return could be closed off and bypassed. The gas boiler was eventually taken out, as it was never used, gas meter gone, no standing charge.

How is this unit one year on? Does it cope ok with heating during cold weather ?

I’ve been looking out for R290 based regular split system air conditioners now that regs have relaxed and allow them - there’s one by electriQ, and it seems like more are on the way: https://naturalrefrigerants.com/the-rise-of-propane-based-residential-ac-in-europe/

Consider upvc 3G instead of 2G. Supply only is £170(3G) instead of £120(2G) for an opening 1m x 1m window*, and it’ll get the u from 1.2 down to 0.7. It’ll be a bit quieter, and even less cold feeling nearby. Likely installation actually costs more than the units themselves anyway. When they’re being fitted, get some decent air tightness foam in the gap between frame and brick; usually there’s sealant on the outside and just a bit of trim glued inside. *https://www.modernupvcwindows.co.uk

We had a trippy circuit for ages, it got worse and worse - the gap between tripping of 6 months, 3 months, 1 month, every week. Tried a current clamp around the combined tails that some internet bod recommended, all the circuits had some, that one didn’t stand out. By the time it was tripping every week I was switching off a few double sockets for a week at a time, trying to isolate what it was - nothing I did made any difference. We had some stuff running on long extensions from sockets on other circuits, as part of this elimination process. In the end I swapped out the RCBO with an identical one. That fixed it, no trips in over a year now. YMMV.

We’ve never really bothered staggering loads to avoid peaks. I have however trimmed the inverter ‘zero’, and that makes a lot of difference. That is, the CT clamp feeding the inverter to tell it what the power draw is, that the inverter is trying to null, and gives a small signal that is easy to swamp with mains hum giving an offset. With most inverters this can be tweaked out such that the smart meter shows 0W or maybe slightly -ve (exporting) rather than slightly importing all the time - this simple change makes a significant difference to the daily peak import. I think I optimised this offset mid April, the pic below shows the peak consumption happening every day before that. There’s still sometimes a high daily peak import - I think that’s mostly the Ohme charging the car at odd times of the day - octo-aid doesn’t understand it’s actually octopus giving cheap hours.