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Does your heat pump expect to connect to the immersion heater? If so that dictates a lot of the controls and you have to work or adapt around that. In my case the ASHP does connect to the immersion heater (though I have disabled all use of that in the settings) and it does so with a control box supplied with the heat pump, which contains a contactor and mcb's. To integrate that with my PV dump controller, I modified the supplied box to single pole switching, so only switching immersion L via the contactor, and then connected a solid state relay in parallel with the (now single pole) immersion contactor switched from my dump controller. The use of a remote SSR for the dump controller was a big motivation for making my own. The immersion heater will have it's own normal thermostat and secondary over heat protection should that one fail. The cylinder mounted thermostat with a probe in a cylinder pocket is to protect the cylinder from over heating when fed from an external heat source, so should be wired to close the motorised valve on the cylinder input coil if the cylinder is overheating.

You sound like you are making it difficult. If you are using a 3rd party cylinder, the immersion will already have can in built safety cutout as part of its thermostat. If you want a diverter as well, I would simply move all the immersion stuff away from the heat pump controller, and do it all stand alone. Then use a standard immersion controller and diverter in parallel. So either diverter or normal timer override can power the immersion. Take power direct from consumer unit.

@Nickfromwales I think this may help - there's width to add the central pillar, by reducing the two side returns. All the supporting pillars around the permeter will be tied in as they are built. At our previous house, we had the garage in the photo - the pillar isn't massive. Apparently the concern now being expressed within the New To This household is that pretty much the entire width of the garage is exposed to the elements once that single door is opened, I personally don't see it as an issue, but it's Himself's baby, not mine!!!! His precious chariot will live in there, alongside the tractor mower and a few other bits. There's a separate pedestrian door in/out as well. @BotusBuild, I wouldn't put the goal post in if we are going for two single doors, simply the normal lintel over each opening. I should have added images at the start, would have made it a little more evident for all what I was getting at.

EDF FreePhase. We have averaged ~16p/kWh over the last month: 7kW Vaillant ASHP, no solar or battery, maintaining 21.5C indoor temp 24/7, no setback at all. We ignore the 4-7pm peak except for load-shifting the dishwasher & washer/dryer overnight.

Are heat pump warranties 10 years or more like a boiler? Genuine question I've never looked in to them

I am finalising the wiring for the Heat Pump install and have got to the immersion. When I originally drew up the wiring I had a 24V contactor in the circuit and all the safety / interlocking done on the 24V side to give the BMS full control. Now I am wondering if: a. Am I allowed to have the immersion controlled by a contactor with all the thermal cutout and setpoint control stats in the 24V circuits managing the contactor. (See Image below) b. Should I consider a solid state contactor - if so which? c. What provision should I make for a possible PV diverter, ie terminals below the contactor or what!

What about if super diluted? Still same?

Had a look at your data and did some calcs so things adding up much better there, you can see the measured flowtemps does lag the calculated ones but not hugely so you shouldn't be burning huge quantities of extra gas even if the flowtemp does exceed the target temp by 2.5c or so under steady state conditions, the boiler output will be outputting ~ 1.0kW extra so say 15kWh over a 15 hour heating day or pro rata, at 6p/kWh?? = 90p/day, not huge?. On for 5minutes Flow 30.6 return 15.6 dT 15.00C Burner 62% 22.32kW Pump 93% 20.00LPM dT 16.00C Flowtemp 31.6C On 15 minutes Flow 50.9 return 29.0 dT 21.90C Burner 100% 36.00kW Pump 100% 21.50LPM dT 24.00C Flowtemp 53.00C On 25 minutes (target temp reached) Flow 60.1 return 39.0 dT 21.10C Burner 100% 36.00kW Pump 100% 21.50LPM dT 24.00C Flowtemp 63.00C On 30 minutes Flow 63.2 return 42.8 dT 20.4C Burner 95% 34.2.00kW Pump 100% 21.50LPM dT 22.80C Flowtemp 65.6C On 35 minutes Flow 64.8 return 46.4 dT 18.4C Burner 85% 23.40kW Pump 100% 21.50LPM dT 20.4C Flowtemp 66.8C On 45 minutes Flow 64.8 return 50.2 dT 14.6C Burner 65% 23.40kW Pump 100% 21.50LPM dT 15.60C Flowtemp 65.8C On 55 minutes Flow 61.9 return 50.7 dT 11.2C Burner 49% 17.64kW Pump 100% 21.50LPM dT 11.76C Flowtemp 62.46C big time gap now as I stopped measuring till it settled to actual target temp of 60'c On 1h35mins Flow 59.9 return 47.8 dT 12.1C Burner 49% 17.64kW Pump 100% 21.50LPM dT 11.76C Flowtemp 59.56C

If you aren't bothered about claiming the grant then you could install a muktisplit A2A heatpump This would give you cooling in the summer and leave the gas boiler for water and backup heating in winter. (summer water could be immersion heater from PV?) You haven't mentioned if you have a gas hob - factor that cost in if you want to get rid of gas altogether.

“If it don’t fit, it don’t fit” 🤠

Picky 🙂

About the same. ASHP shouldn't last as long as good fridge. But technically a heat pump produced today will be over taken efficiency wise every few years. A poor boiler or heat pump install, is unlikely to last a a good one. So many variables.

Anybody want to have a stab at how long an ASHP will last, vs a good quality gas boiler? This also needs to be factored in.

The quick fix here is to grab the screw and put it back in. Slows the flow, or if you’re gentle can actually nearly stop it altogether. Just looking for a chicken emoji lol.

Downside is by the time the pillar is built there won’t be the width left to install 2x 2.4m (OP is 50mm shy on that before adding the pillar width). @New to this A pillar will be fragile unless tied in by design, so would need to be a decent offering. The first time you bumped into a single brick wide pillar it would fall apart. You could fit a 100x100mm box section steel post, or even 150x150mm, and then dress it and fit brick slips to it so you’re less than 150/200mm wide but strong as feck. This wouldn’t affect your existing plans / designs, and means you could revert back to original. Steel would just have some tabs top and bottom for fixing it in robustly. FWIW, I’d need a very good reason to fit 2 smaller doors vs one useful larger one, but I’d also have a side or rear door for occasional visits. Standard size garage doors are pretty pants, but I guess moot if you’re not putting a vehicle, or maybe only one vehicle in there? Pointless unless you can comfortably open the doors on the car.

As I'm using clay paints, which may behave differently to the scrubbable paints, I use the auro plaster primer https://www.auropaint.co.uk/product/plaster-primer-no-301/ It goes on a treat and works far better than mist coat. but as it works with emulsion, it might be fine.

Okay 1 more. First self build, over 20 years ago now. Originally planned a square shower tray. UFH pipes laid out to suit that. Floor marked with big marker pen showing where every single pipe was. Changed plans. Decided on rectangular shower. Waste in a different place. Cutting the hole for the waste, a fountain of water started to come from under the floor. Yep I had failed to see my own markings and cut right through an UFH pipe.

Many years ago as a lift engineer's mate. Went to a site to help out. Governor was spitting feathers and everyone was coming in for it. One of the not so bright labourers had been tasked with opening out some holes in a load of plates. He'd made himself a "bench" by stacking a couple of cable drums on top of each other. Unfortunately these were full rolls of the specially ordered flat form cable...

Starting from a position of no heating yes. Doesnt add up if you have a nearly new gas system already. Obviously if you go DIY as you have done, then that skews the figures, but for most, who are just paying, (probably grossly inflated prices) its makes no economic sense. Just wait for the boiler to die, then do it. Im in the same position, albeit with oil. And i would DIY it. But it still makes no economic sense. I have some re-cofiguring of the heating to do, so i will provision for an ASHP. But i wont be fitting one until i have to or the economics swing in its favour.

Thank you. That’s a well done for J. I did the polystyrene and the (*&#£*!!! ing) PIR in the floor. J does the walls.

One beauty of going this way, is if you do decide later on (say in a few years time) that the original full width garage door was the way to go, you know knocking down that middle pillar will not do any harm 🙂 I'm trying to think of a downside but can't think of one.

Just looked back at our quotes from our local Jewsons. EPS70 was less than £47/m3 PIR (foil faced) was less than £87/m3 Both for 120mm thick 2.4m x 1.2m sheets held in stock locally at their suppliers.

Thats interesting. I need to buy more for my workshop. The previous part i did in 100mm (seconds) with 100 x 50 battens. Was going to do 50 +50 this time to reduce the bridging effect of the battens. Though the saving on timber by using 50x50 studs might offset the PIR increase? Plus of course depends what seconds and Co have available at the time.

Is that assuming a BnB floor with the underfloor void being the same temp as outside? One of the reasons I was pleased to go first a solid floor was that the ground under would be a more constant temperature possibly 7C.

Not a confession, but ... Builder sent his chippy to site with some youngster in tow (doubtless very cheap labour for the builder). Chippy sets the youngster up to put some battens on the wall - simple enough. Youngster proceeds to drill all the way through the concrete block wall and out the other side. Which I discover some days later when wondering why bits of new plaster have fallen off the wall on the other side. Multiple holes right through the wall coming within mm of drilling straight into the back of the new £2k boiler wall mounted by the plumber days before and the cylinder expansion tank.