ReedRichards

For good reason or just tradition? dT=5 C and flow rate F is the same as dt=20 C and flow rate F/4 in terms of power supplied to the water. Modern "Low Temperature" gas boilers operate in a similar temperature range to heat pumps but AFAIK stick to the larger dt and lower flow rates of a traditional gas boiler. Clearly a smaller dT means the average water temperature is higher so you get more heat out of your heat sources but Low Temperature gas boilers seem to manage with a larger dT so why not heat pumps?

Well here we are on 1st April and there have been 2 days so far this year when my solar generation was enough to charge the battery and still leave some left over to heat the DHW. On most days my solar power is being eaten by my heat pump almost as fast as it is generated. Granted, the ASHP is heating the hot water as necessary, as well as the house. But if it was only heating the house I don't think I would be exporting any more electricity. Perhaps my 2 person household is not normal?

I've never understood why heat pumps need such wide pipes and nobody here is saying. You can achieve the same volume flow rate in a variety of pipe widths so for some reason it must be the speed of flow (metres per second) inside the pipes that is the important factor. Perhaps the pipes inside the heat pump unit are wide and the pump isn't powerful enough to cope with a reduction in pipe width? But if that's true then there's only one right answer, which is to match the internal pipe size, anything wider would just be spending more money than you need to.

No, it's a 12 kW ASHP That's good for you but it's going to take a lot longer to heat the same amount of hot water compared to mine. I don't actually have a solar diverter, they're expensive I didn't think I could justify the cost. I just switch the immersion heater on and off using a switch that is controlled by WiFi and programmable. If my battery is near to full charge and the sun is shining I switch it on; the battery covers when the sun goes behind a cloud.

When my heat pump heats the hot water cylinder it heats it to 50 C and draws up to 6 kW of power. When my immersion heater heats the hot water it heats it up to around 65 C and draws 3 kW of power. So I can make my hot water hotter with the immersion heater and since 3 kW of output is within the capability of my solar panels (aided by my battery) can do this completely free. Or I can supplement my solar power with imported electricity, use the heat pump to get cooler hot water but then have a lot more solar electricity to export. In my case I am paid for deemed rather than actual export so the immersion heater option is a clear winner.

Presumably that's something to do with the meter box being a more convenient location than your CU. There's no technical reason why they cant use your RCBO unless more than 32A are required. No.

The expensive thermal stores that use a phase change material instead of water describe themselves as heat batteries and that is an apt description. The cheapest heat battery that you will find is a tank full of water and last time I looked it was much cheaper than an electrical battery in terms of cost per kWh stored.

What you can't do with most oil boilers is get them to modulate; they're either full-on or off.

If I were you I would put the new unvented cylinder where the old one is for now then relocate it when you make your loft into a habitable space.

Even the best-insulated hot water tanks lose heat. If they are inside the heated fabric of the building that lost heat goes towards heating the house so it's not wasted at times when you actually want to heat the house. Heat lost from a tank in the eaves is just lost, although maybe not if the tank is relocated into a cupboard that forms part of your new habitable space.

Can I presume that the first figure should be 2.6 kWh (kWh being a unit used to measure energy)? Whilst the second figure is a peak power of 2.5 kW?

I've stood in front of my heat pump, which is probably a bit larger than yours, but never found the "wind" it makes to be particularly strong, nothing compared to the actual wind on a breezy day like today.

This doesn't make sense. I would think you could buy an ASHP, wear it out and replace it with another one before you reached the cost of installing a GSHP. In the long term a GSHP might be cheaper to run but you will see an immediate saving if you get an ASHP, which could be eroded over time.

I asked because you may or may not get any improved economy from a mix of UFH and radiators, as was discussed today on another thread.

Do you want the underfloor heating for aesthetics/space-saving (no radiators) or comfort or economy of operation?

No, you're absolutely correct. What you want is an ASHP that reduces its flow temperature when the radiator zone is not calling for heat. Given the different response speeds of UFH and radiators there could be quite a lot of time when the UFH needs a bit of warmth but the radiators don't need any.

I could be wrong but I've familiarised myself with the controller and read the Product and Installation Training Material and I don't remember seeing anything on how you would set different flow temperatures for different zones. Now my system overrides the LG controller with a third party controller which means I don't get all the features that LG controller could do on its own (such as the poorly-documented Load Compensation). So possibly the capability you need is there but not visible to me. You can read the Training Material here (bottom of page 11):

I don't know if this has been mentioned on this thread or elsewhere but I read on another forum that an ASHP will now boost your EPC rating, rather than downgrade it as hitherto. This had been flagged as a change that was coming but it seems it has happened now.

I have an LG heat pump and by and large I am pretty pleased with it. But mine is a monobloc unit. I've never understood why a split unit is thought to be a preferable option, it consumes valuable indoor space and adds complexity. If you have a mix of radiators and UFH then the LG heat pump is not smart enough to let you derive any economic benefit from the UFH, it cannot reduce the target flow temperature when the radiator zone is off so you need to maintain the same target flow temperature at all times and this is likely to be higher for the radiators than the UFH needs. Some things to think about with regard to the solar panels: Would you wish to export more than the 3.68 kW for which DNO permission is given routinely? Will your inverter let you do that? Does your inverter allow your house to use more than 3.68 kW at a time? Are the batteries on the DC side or the AC side of the inverter? Would you want power from the batteries in the event of a mains failure?

Perhaps the fact that a gas turbine power station converts gas to electricity with an efficiency of just under 50%? So if we already waste energy like that, why not find other was of wasting energy?

If you buy a modern "low temperature" gas boiler, my understanding is that it is set up for a 20oC drop between flow and return. If you buy a heat pump it is generally set up for a 5oC drop between flow and return. For the same rate of heat input this would mean that the heat pump has to have a flow rate four times as fast as the gas boiler. I don't understand why there has to be such a disparity; perhaps it's just different traditions? But heat pumps use high flow rates so need larger bore pipes.

So the 0.7% per day figure represents a lower bound on real world leakage rates. The physics of the molecule means that a pipe that leaks methane at a trivially small rate will leak hydrogen a lot more readily. Nobody would care unless the leaked hydrogen builds up and then causes explosions.

I don't think this figure can possibly be known in the real world, the best that could be done at present is a trial where the hydrogen is introduced vey close to the point of use.

Weather Compensation/"Water Law" doesn't apply to heating your hot water so if your space heating is off then the Water Law numbers should make no odds. Looking outside here, we've had a hard frost and the pond is frozen so you must be living somewhere that's a lot warmer than where I live.

Hydrogen is a very leaky gas. Is it really more viable than a heat pump?