Thanks for your update. I am so glad for you that you have finally found a resolution with the oil heating system… after 5 years

I just got the electricity bill for this month and it was £388.00  - 3/4 of that was the heat pump, which is just too expensive to operate. I know this because it is a cascade system.

I’ve been advised that a monobloc would work, but I would need to have new heating system pipes put in and that could mean lifting floorboards. The pipes from the heat pump have a dia of 25mm and these are reduced to 22mm into the pumps before being reduced further to 15mm. This means that the flow rate has to be increased substantially in order to successfully transport the volumes of heated water required to the radiators. In order for the system to work properly they should be all 22mm and not 15mm. So the Heatpump has to operate at higher temperatures and at higher flow rates - this uses energy which results in a COP of 1.3.

I continue to investigate supplemental systems and in the meantime I will contact the HIES governing body next week to begin to get some resolution for my system through that route.

Great to hear your news

@jet sorry to hear you are still struggling with your system. At one point in my complaint they advise me to have an additional 8 kw unit bolted on to my system,creating a cascade unit. The other way round to what you are being told. My ASHP system was designed to run at 55 degrees which the unit installed should have been able to run.My costings were given at that flow temp. My pump just couldn’t reach that flow temp when it was 0 degrees outside.

I don’t understand the ins and outs of pipe sizes but my system sounds to be similar to yours  28-22–15 at the rads.The oil boiler is set at its lowest setting of 55 degree flow ie the same as the design temp of the ASHP system and it works really well. Napit refused to send an independent engineer to look at my system so I will never know if the pipe sizes were anything to do with it or not. I suspect not and that it was just the ASHP that couldn’t deliver the require flow temp not even near. It is all so confusing to be honest and I don’t think that us as consumers should be the ones left to fight to have it put right. I paid for a system that would heat my property to 21 degrees with a running cost of 8250 kWh per years not between 13000 and 15000 kWh to heat my property to 16 degrees. ( sorry to rant). I am not suggesting oil to anyone one but my new system warms my houses easily and cost less to run and if it should break down there are about 10 local engineers that could fix it rather than 1. I really hope you find a solution to your issues soon , it is so stressful. Good luck.