J1mbo

I’ve read this several times recently but I’m struggling to correlate this to spot or futures. It’s definitely counter intuitive thatgas delivered in a lorry could be cheaper than piped gas.

To give some numbers, the system I have fitted has be working at about 6.1p per kWh effective throughout Nov/Dec/Jan. Those are on the price cap for electricity. That's pretty much exactly equivalent with oil, which is currently about 60ppl. Design flow is 44°C at 0°C outside, so not that much different to the scenario here.

It definitely won't be cheaper than gas. Electricity carries as 25% tax (climate change levy).

The circulating volume needs to be enough to avoid short cycling and 132 litres may well be not enough.

The ASHP market is currently tiny compared to oil/gas - and anyway, nice stuff (especially tech) costs money. Octopus have stated that they will be offering ASHP installed (presumably Vaillant based on their marketing videos) from £5,500 in about a years time. As the market expands the prices will tumble, as with any tech.

Cost £14k, RHI £12k, cost £2k. Compared to eg new oil system with tank. Cost maybe £8k, RHI £nil. For those that have access to the capital, RHI has made it a no brainier.

Nice, I'm quite interested in this as it would be handy to 'hey siri turn on the hot water' when certain members of the household have used it all up.

Degree-minutes is used by the controller to regulate energy supply. It's not related to anything the VRC700 is doing.

Why not give Vaillant tech a call. They are really helpful.

so the flow temp is coming down too quick it seems. Are the temperature readings from the outdoor and indoor (vrc700) accurate? An offset can be applied to both individually in the VRC700.

(20+33)/20 = 2.65. The energy used by the compressor is mostly stored in the gas.

Vaillant reports the energy consumed (E) and the environmental yield (Y). The COP is (approximately) (E+Y)/E.

How are you computing the COP

^^ definitely as above. The price of these systems will likely come down dramatically over the next year or two, but that will be offset somewhat by inflation. The system are R290 based but I've not heard of the vendor before. Something to consider is what controls are going to the attached to it. Does it provide flow control based on weather compensation (reduces running cost) and room temperature (increases responsiveness) for example. Does it provide proper integration with your solar systems? Is there a phone app and has this been updated any time recently? Is the sizing consistent with what's already there? How long is the warranty on it? At 12 years it's definitely running overtime and the figures don't look too outrageous to me provided it's a quality product with at least 7 years warranty (to match the RHI) and can *definitely* be installed, commissioned, and logged with the RHI before the deadline. Also check it is MCS accredited obviously.

Maybe bump the curve to 1.0. Yes it will increase the flow temp as the deviation gets further away, but 0.6° is not very much. Increasing the radiator circuit pump speed will reduce the dT across them. If it's somewhere near 5° as it is then it's probably about right.

It looks ok to me - there's literally one cycle per hour. 10 minutes is often cited as the 'rule of thumb' minimum. Likely the total radiator output at the set point was less than the minimum heat pump output, meaning the set point was exceeded and eventually (at 0° minutes) the system shut down. That the temperature was not maintained suggests that the curve is too low.

I've never had to reset or restart mine. I'd consider calling Vaillant if you are finding this. The Internet gateway (VR920) if you don't already have it is quite handy as it displays good information about the system status in the event there is or has been a fault. Is there anything connected to the 'supplier input' (EVU/ECSO terminals)?

What controls are attached?

ah gotcha, yes it seems so but then again 11kW for 230m2 also seems like a lot unless perhaps there is a lot of hot water demand.

It should be set so that the desired temperature is just reached and maintained. The idea is to have the lowest water temperature possible.

Fixed flow temp is the worst possible configuration for ASHP. This is why the controls have sometimes almost endless configurations all centred on reducing the flow temps whenever possible. That said, if it’s an underfloor heating setup needing only 30* flow anyway, then clearly all that complication is going to yield minimal gain.

@rhymecheat have you been able to read the flow and return with the infrared for the heat pump and also for the backup heater as yet?

Thanks for the ideas and links. The current controller is 4kHz which looks great to me even at minimum brightness, but that is my only point of reference I have. The tape is in plaster-in aluminum profile in the ceiling (i.e. directly shining downwards into the room) and has opaque diffusers fitted. It is 7W per meter, fixed 4000K.

TBF it's probably the semiconductor shortage, which is affecting everything electronic.

Thanks for the replies! There are six lengths of single colour 24V LED tape totalling 70W. The current driver is 100W rated. Im sure there are better products to use and that’s exactly the ideas I’m looking for. Has to work with a simple knob on the wall but also be HomeKit controllable however so - and of course not flicker at all.