JohnMo

We have balanced MVHR, WBS with an external air vent connected to to the stove. Would have thought a disconnected air supply, is just an air leak in to house, not really understanding why you want it in an airtight house, with MVHR. But everyone to there own thoughts on that. Never experienced anything stuffy in the house (with or without stove on), have baked myself when we first tried the stove with room temperatures at over 27. Buts its just a matter of getting the stove burning, very little air and not much wood, to controls heat output. Don't select a stove with a high output. A house that requires circa 3kW to heat at -5, doesn't need a stove that puts out 16kW for example. When stove is off, just select air supply off, so no un-necessary air movements. Simple

If you no idea of the basics and the equipment needed, should you being the install? Basic parts Panels plus mounts, optimisers (option) Connectors Suitable DC rated cable, suitable crimper for making up connectors DC isolation switch, even if inverter has one Inverter AC isolation switch Meter

Sorry I missed typed. Electrician doesn't need to install, but as you say declare it's compliment.

Just point of note even without mcs approval, in case you hadn't realised, your electric install has to be by a registered electrician. Their certificate number is required for the G98 form.

@ReedRichardsYou could have few issues - Looks like you are short cycling - heat on for a short period, forced outage for 10 mins. Issues that cause short cycling are Your buffer could be too small. Lots of zones combined with no buffer or buffer that is not big enough to compensate for the smallest zone open. Do you have lots of zones or just one? Open zones doesn't meet or exceed the min flow rate for the heat pump. Or is the flow temp to high and room temp keeps hitting a thermostat set point - switching the HP on/off. Either way somethings not right. The ideal of WC is you don't have a constant set temperature, but you have a couple degrees reduction in temperature during the night.

Just use a Salus SQ series thermostat, hysteresis can be set to 0.25. it can also be set to to learn your heating response time make adjustments to how it reacts. Good for radiators not so good for very low temp thick screed UFH. Or just change over to weather compensation and don't use thermostats.

I've use made2measure. Not installed yet.

We did a couple of small walls in our ICF and used a mix on demand lorry, more expensive than ready mix. But we did a couple cubes, by barrow and buckets, we also did a few other concrete jobs at the same time, all different grades and slumps, all from one lorry.

Ours was £580, good job it wasn't £1200 as we had him 4 times

15kW is the correct units, before @SteamyTea comes back

The sip build may bolt supports to the floor, so would be worth checking with contractor. Holes in floor, or UFH pipe?

So are you using 2 hours x 11kW or 22kWh per day for hot water? That doesn't sound right?

At that price is worth installing? Rough estimate is 3.5kW installed is 3000kWh year. So about £1000 per year offset if you use it all. If you export a fair bit at a couple pence a unit, much lower yield cost wise. A 345w panel is about £200 delivered, do the maths. So £2000 for panels, £600 for an inverter, plus mounts and a couple of switches. Sounds like an installer taking advantage.

No, but seems to be performing well. Last winter was a disaster for gas consumption, underestimated what low temp heating needs to support it. Lots of short cycling, house way too hot, then too cold most of the time, didn't appreciate how to manage a thick (100mm) concrete slab, hoped smart thermostats would help, but they just messed things up even more, the floor response time was outside there logic. So operate as a single zone, with loops balanced to set room temperature

Only had the system running in this configuration during Oct (off at moment due to warm temperature). But have consistently delivered an average of 0.5kW (based on actual gas consumption) heat into the floor over a 27 day time period. House is 192m2, UFH pipes at 300mm centres big buffer. In NE Scotland. In the depth of winter hoping for a 2-3kW gas input, but time will tell.

Sorry you really need to read up on condensing boilers theory. What you have been told is just wrong and applies to non-condensing boilers. Not sure where your getting my boiler is running at 54+ degs from, last time I looked while the boiler was firing it had a supply temp circa 28 and return 23/24. If it gets to 35 it is forced to cut out, by the settings. Only time it goes above that is for DMW as its a combi.

Never really seen why people fuss over PV efficiency if you have room to install them. PV efficiency is w per m2, nothing more or less. BUT - Getting them at a good price, that is the important thing. They should be cheaper than high efficiency panels, because they are using an older technology. Another thing to ask, are new - old stock, as some of their 20 year life may have expired. In that case I would be wanting factory fresh, not something that has been hanging about for a number of years.

Yes running a buffer, but the buffer has no thermostat, so just floats at supply temperature, so is never hotter than target flow temp. Plumbed as a 2 port buffer. Boiler fires up when it sees the return temperature drop to a level where its happy to fire up, keeps firing until it's no longer happy. On an average 10 degree day, fires for 10 mins, off for 2 hours. -5 day, on for 30 mins off for 30mins.

The idea is the flue gas passes through a heat exchanger, it condenses, gets drained away. The process has a phase change from steam to water, the latent heat is captured by the heat exchanger and passed to water increasing efficiency. The acidic water goes direct to drain after that and does not go through the flue. A condensing boiler working correctly has no steam coming out the end of the flue. My boiler is running at target flow temp of 26 to 29 degrees depending on outside temperature. So they do go below 35 degrees.

Take a look at the efficiency and recorded flue gas temps at low flow temps. Screenshot from the same manual.

Direct cut and paste from a condensing boiler manual. "The boiler is equipped with a compact stainless steel heat exchanger with smooth pipes. It is a well thought-out principle using sustainable materials. The boiler burns (natural) gas to supply heat. This heat is transferred in the heat exchanger to the water in the CH installation. The rapid cooling off of the flue gases causes condensation. This results in a very high efficiency. The condensate that is formed, has no negative impact on the heat exchanger and it's operation, and is removed through the internal syphon."

That may be true for a non condensing boiler, but since 2005 it has been illegal to sell or install a non condensing boiler. If you boiler is older than that it may be true. If newer than that he is talking rubbish and really needs to get his facts in line with technology from 20 + years ago.

Thought they all were these days.

So again to compared apples with apples, circulation pumps are on bothe a heat pump and a boiler, in either the pump can be inside the box or outside. Ignition is on for a few or less seconds. Fan will be on almost all the time the boiler is firing. So it's 35w/h X 4 x 180 ( days in heating season. So nearer £8.50. plus an hour a day for DHW, so about £140 over 13 years So close to £150

Basics are, the smaller the differential, between flow and return the more heat that goes into the floor/room. You can do this by increasing a loops flow rate. The opposite is also true, bigger differential lower heat output. Decreasing flow rate increaces differential, to output. So it's just a matter of getting the balance right. Remember Wunda and other just want you to buy more products. I got all my UFH from outsourced energy, good prices and products.