@saz, was your ASHP installed by a MCS accredited installer?  If so they should have done heat loss calculations to ensure the pump was sized correctly for your house and radiators.  If your ASHP is undersized it could certainly lead to higher bills as it will be working flat out, which will be less efficient.  Do you know what your annual heat and hot water demand is on your EPC?  

If the immersion is coming on the heating flow temperatures and/or hot water settings could be too high.  Most ASHPs will struggle to heat water to much more than than 50 degrees; if it is asked do so it needs to use direct heating like the immersion.  You want the temperatures as low as possible to maximise efficiency.

Obviously you need to get any leaks, etc., fixed.  But as steps you should (1) set the hot water to no more than 50 degrees and (2) put the heating flow temperatures on 'weather compensation' if your system has this (and most new ones do).  If not, set the heating flow manually to 45 or 50.  If you don't know how to do this, please ask again.

Hi @KevM  It was installed by an accredited installer but I don't understand why they sized this pump at 5kW when my old Dimplex was 12kW. It is a high temp air source heat pump, which again, I don't really understand as I live in a fairly new-build with good insulation etc. and my old system was an ordinary low temp one which the Underfloor seemed to work better at (there is no blending valve on the manifold). My radiators were sized larger for my old system. I had an immersion on the old system too (for the legionella cycle) which generally only came on for that, or if it was very cold, it was on a fused spur also, but this new system is using the immersion alongside the heat pump already, not just for the anti-legio and it shouldn't in theory even need to use it for that according to the manufacturers own docs? It's wired in to the module. I don't have access to the EPC or heat loss calcs. The hot water is set to 50 degrees, I will have to ask installer what flow temp it is set at. I've done some usage comparisons with my old system and it's just so much less efficient and expensive.

Our system went on the fritz last night, so we're without heating again. Smell of glycol in the utility room, pressure on the expansion vessel has dropped to zero and no visible or obvious leaks. Getting hold of a plumber is a nightmare (as always). So it's back to the fires for today and tomorrow and hopefully Global Energy Systems can get someone out to us early next week.  

Oh no @editor Am I right in thinking you have the Arotherm plus also? I'm using a portable radiator and boiling kettles again at mo until this immersion issue of mine is sorted. Do you have an immersion on your system? If so, is it on a fused spur?

@saz, we have a unit from Global Energy Systems - a British brand. We have an immersion connected to our solar PV so we were able to reheat out hot water at least. The fires are on and the heaters all be in the bedroom tonight connected to a smart plug to come on and go off throughout the night.

If there was a leak, it would have been better because we'd know what were dealing with - but we can't ID the issue. 

@saz, it sounds like you are familiar with ASHPs.  The Arotherm plus claims to be able to heat to 60 deg plus or so efficiently rather than the 50 plus from others.  It's supposed to be able to cope with very cold weather better and/or run with smaller radiators but it sounds like something isn't right with yours.  It's definitely worth checking the flow temps.  If your house was heated by a flow temp of 50 degrees (or whatever) then it still will be irrespective of which heat pump supplies the energy. 

Unless your HW is set very high or it's very cold weather (well below zero) your immersion shouldn't be on.  As you say, your high temp Arotherm should just about be able to to do the Legio cycle itself so you should definitely have a word with the installer.  Is the heat pump heating the HW at all?  Can you turn the immersion off and see what happens?

We have a smallish 4 bed bungalow that's quite well insulated and our installer thought an 11 kW pump was too small.  We have a 14kW one.     

@editor, oh no, just the wrong time of year for that to happen. Hope you get it sorted soon.

Posted by: @editor

Our system went on the fritz last night, so we're without heating again. Smell of glycol in the utility room, pressure on the expansion vessel has dropped to zero and no visible or obvious leaks. Getting hold of a plumber is a nightmare (as always). So it's back to the fires for today and tomorrow and hopefully Global Energy Systems can get someone out to us early next week.  

Hi Mars,

Looking on the bright side, at least it did not happen in the depths of Winter. Have you tried re-pressurising your system and looking for leaks, also the rate by which the pressure falls will give some indication as to the size of the leak.

@derek-m, we’ve had two outages in back to back years in December so an October outage is definitely better. 

Partially good news is that we’ve found a wet spot that’s originating from behind our oil boiler (the back up) which indicates something’s gone wrong there. Contacted about six heat engineers yesterday who just aren’t interested in coming out or just cleared our calls.

Home Emergency insurance (AXA) equally useless in sourcing anyone. Hopefully Global Energy can send someone out early next week. House was snug though with the fires going. 

@kev-m, it always happens in winter. Three years on the trot, but like I said to Derek at least it’s happened in October as opposed to December.

Hi

New member here looking in earnest at ASHP for our imminent new self build.  I had assumed that it was a no brainer but am beginning to wonder…

I am particularly struck by how much ‘tinkering’ and hands-on adjustments have to be done just to keep it running - clearing filters, dealing with leaks, data monitoring and adjusting settings etc.  Is that because the systems are more fragile and unstable than the marketers would have us believe? 

We will be retirees and planning on using this system through into our frail old age, so want a system that will give us straightforward, reliable warmth as and when we are old and infirm.  We are beginning to think we would essentially be early adopters of a technology that still needs lots of maturing and therefore not a good idea at this stage?

Would be very interested in your views.