Beelbeebub

You usually need to buy the camera too, I use thr "top Don" one, it just plugs into your phone and away you go.

The ufh should be able to get those rooms warm if it did before. The flow temp shouldn't be very high ie a HP should be able to achive the temps. My suspicion is too. Much flow of going via the radiators, which is shutting down your HP, the UFH then doesn't have a supply of warm water to "top up" the loop temp via the mixer valve and then they underperform.

I had a cottage where the radiator in the hall was absolutely scorching and all the other rads were like warm. The boiler short cycled and lots of gas was burnt. We closed the valve on that rad right down and all the rads became warm, the boiler stayed on for long continuous burns and the cottage was warm for not much more money

As I said the other option is one rad being "too open" and starving the other ones.

Either your emitters are very undersized - thr ufh loops should be OK, the whole. Point of ufh is it being a big emitter. Maybe your rads are too small? What type are they? Single panel, finned? Double panel double fin?. How big are they? Rads for HP should be bigger than what is typical in a boiler heated house. Your plumber should be able to tell just looking - 'they look bigger than I wound expect" or "nah, looks. like I. Would expect for a gas boiler house" (ie too small!)

Potentially the Vito boiler was supplying higher flow temps and each emitter was outputting more. This is why radiators and pipes sometimes need to be swapped for bigger ones when a HP is installed. Get an IR thermometer (better yet an IR camera for your phone - can use it to track down heat leaks in the walls too) Check your rads, your (heated) floors. Is there a rad that is especially hot, in particular if it's flow and return are very close - they should be 5-7C different. It's possible one of the rads is "short circuiting" the flow, which cause the HP to shut down (as the flow and return are too close) and your overall heat output to buikding is lower plus less efficient because of start stopping.

Link to the manual. https://trade.centralheating.co.nz/assets/resources/Chofu-Operating-Installation-Manual.pdf

What are your radiator sizes? Are the ufh heated rooms warm enough? What is your floor temp in those rooms(cheap laser thermometer will do) Look at what the return temp (parameter 00) and output temp are (09). Ideally they should be 5-7C apart. If the return is climbing closer to the output then your emitters aren't getting rid of the heat quick enough. It could conceivably be a radiator loop that is too open and the flow is all rushing thorough there, hardly losing any heat.

This may not be a good idea, temps that high may cause issues with the slab and floor coverings - the mixer and pump system is there to run the UFH at a lower temp than the rad system. IIRC thr max floor temp is supposed to be 28C, running at those flow temps will almost certainly result in parts of the floor getting hotter than this.

The suction temp is the temp the refrigerant gas is when it leaves the outside coil and enters the compressor, it is then compressed and leaves as a hot gas (discharge temp) So a suction temp of 4C means the air moving over the coil outside was probably at about 4C Then 88C gas was leaving the compressor. Which seems a bit high for heating mode, I would expect it to be more like 50-55C for a 45C (water) flow temp. That suggests something might not be quite right.

The first thing to note is that this sub zero weather will cost alot to heat especially with a HP. For example, my gas consumption is about £8 a day in these conditions. You say parameter 21-00 is set to 0. This is fixed flow temp. Look at parameter 20-01, that should be the temp your HP is outputting. The default is 45C, and maybe that is too low? It will also have been too high for the milder weather. The default for 21-02 is 45C, so the fact it's been set to 50C implies someone has changed it - possibly because your heating system needs more than 45C in these conditions.

Could you install something between the cylinder sensor and HP that basically tricks the HP that the cylinder is at temperature after a power cut? Depending on the sensor it could be as simple as a relay and resistor.

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.

JohnMo's solution sounds nice and simple. If you do decide to go for mechanical ventilation, I have used the ventaxia sentinel kentic series a few times now and been happy with the price/performance. Build quality seems pretty good and (hopefully) spares & support should be OK given they are a UK company. 🤞 I use the radial 75mm smoothbore ducting with manifolds for ease of installation and reduced noise between rooms. For some properties I have put a supply and extract in opposite corners of the room to get around the issue of undercutting doors etc.

That's good, thought they ought to include that in the main table figures rather than as an extra. That way they could include the cop. I have seen various ways of showing the performance of HPs but the best (IMHO) is to have a outside temp / flow temp table with each "cell" giving power, input power and cop. It then had 3 tables giving those figures at the maximum, most efficient and lowest outputs. There was some shading on the cells where output was being affected by defrost. That would seem to give all the info needed.

You'd be surprised. If the leak was in thr 1st floor or loft, I would expect you to see something. But if it's the ground floor, depending on location and construction you might not. A property had a persistent leak. Half a bar a week. No sign of water. Clue cam in autumn when kitchen windows had bad condensation. Check with humidity monitors showed high humidity in kitchen. Eventually found a failed joint leaking to under the kitchen floor. The construction was a oncrete slab, with 2" timber battens, then floorboards, a 5mm ply layer and then lino. When we lifted the floor there was about an inch of water. If you have a suspended floor or even a slab, water could be leaking and you not know. Get hold of a couple of humidity meter (these are good https://amzn.eu/d/bMbXgA2) Stick them in varouhs rooms for a few days and see if you can find one that has higher humidity than the others. That may give you a clue.

I'm not sure "all dc" would include low voltage stuff like door bells. I think (and am happy to be corrected) that under 50v DC is low voltage and different regs apply - so single insulated is fine. This would prob apply to the single panel type "camping" systems people stick on vans and the like. But for the high voltage DC you get with large arrays a different set of regs apply and they say DC must be double insulated. Hence using special solar cable rather than regular 4 or 6mm 2 core. I imagine you would need similar if you had another high voltage DC application eg some sort of machine tool or something.

That's a serious volume of water being lost. If you don't know where it's going (eg a leaky prv is dumping it down the tundish) I'd be really concerned about damage to the fabric of the building. Something somewhere is going to be soaked and that is never a good thing.

The cables have a DC rating because you can stick DC down any conductor. But the UK regs say that cables that carry DC must meet certain requirements around insulation etc. Specifically the conductors need to be double insulated whilst they can be single insulated for AC. Here is an armoured AC cable. Notice you have: Copper conductors Layer of insulation (the coloured bit) Packing material (beige bit) Armour Outer sheath. Here is an armoured DC cable Copper conductors Layer of insulation (white) Layer of insulation (the red/white bit) Packing material (beige bit) Armour Outer sheath. Notice the two layers of insulation around each conductor You could use the top cable, it would physically work, in the same way you could just bury an extension flex in your garden to power your garage. But it wouldn't meet the regulations. For that you need the specialist cable.

Yes, that's fine. It"s what my set up uses. If my panels were on the garage and my inverter in the house, then I woikd need the specialist DC SWA to carry the DC between garage and inverter. My understanding is the issue with carrying DC along standard SWA, it that DC needs double insulated conductors and standard SWA is single insulated.

https://www.doncastercables.com/cables/20/89/PV-Ultra--/PV-Ultra-----Double-Insulated-Multicore-DC-Cable/ The do 4 core so you can have 2 strings if required. Regarding upgrades it depends a bit on which panels you're putting in. Current "mid range" panels are in the 450w range with some premium panels going over 500w, a few years go the 450w panels were premium and most were 400w or lower In 10 years time the cheapest panels might be 550w and the premium ones 650w So if you reolwce/upgrade your current will go up even if your array stays nominally the same. Also we don't know what planning will do in the future, it may be they change the permitted development allowance and you could add more panels. Be nice if the cables were already sized for that, especially if relaying them would be a faff - if the route would be a doddle to add an extra cable don't worry too much. But if it"s a sod, just do it once

I think it's that the regs require the conductors to be double insulated within the armour. Ie you take double insulated conductors, then pack them into an armoured sheath, then wrap that in insulation (which is mainly to protect the armour) Most SWA is single insulated inside the armour ie each cable is single insulated, Ie you take single insulated conductors (like you woikd find in a twin and earth) then wrap those in the armour. I think it's because DC shorts between conductors are much worse than AC for the same voltage and current. So the individual conductors need that extra level of protection.

Chunkier DC cables gives you headroom should you upgrade to more/better panels in the future. The resistance of 6mm cables, about 2/3 that of 4mm2 (and 1/4 of the 1.5mm cable) is lower which will reduce your i2r losses (not as much as lowering your current but there isn't much you can do about that) There are DC specific armoured cables now (the common AC ones are not suitible for DC) which makes doing the runs much neater and easier.

So £60 each or about £200 per kw? Roughly halved in price and doubled in output. The same money now buys you 2x the output vs 2 years ago, in the same footprint! Wow!

Sorry, I meant the old panels. As you say we are nearly at £100/kw before vat now. I was wondering what the ratio was when you put the orginal panels in.