Bashers

I've got exactly this issue on my ASHP which I'm raising with Daikin Mine's a pretty simple heating only setup with a single LWT set at 45 degrees going via a plate heat exchanger, so quite a small primary loop. Above 8 degrees outside, the unit cycles between on and off as requested "normally" When the outside temp drops below 8, the unit drops the LWT to 35 degrees and keeps the unit on: In terms of power usage, I've looked at the period between 22:00 on the 19th and 02:00 on the 20th. Each 90 second burst of running uses about 30wh, which it fired 7 times in that 4 hour period. So it uses 210wh over those 4 hours. I know some units get a 180w crankcase heater that run permanently, 24/7 all year I'd love to know what setting they changed? Did they turn the freeze prevention off? Did they leave a new system config report? Did they update the installer manual with the new settings (they should have)? Ashley

Those are reassuring graphs, thanks

Ok, so ive found the detail of this EU labelling here https://www.rehva.eu/rehva-journal/chapter/eu-commission-adopted-energy-labelling-criteria-for-space-heaters; Even more unclear now. From actual ASHP users, can you "hand on heart" say your heating Kwh usage has gone down by 66% for a SCOP of 3, or only 20% for an efficiency of 125%

I've been looking through specs of ASHP pumps and I'm confused (&concerned) by the "Efficiency" line in this table for a Daikin EDLQ05CV3: Space heating (Average climate) 55°C Class A++ Efficiency 125 SCOP 3.20 Publicity would have you believe that for every watt power consumed by this unit would result in 3.2 watts of heat "SCOP 3.20" That's what I've been believing and running calculations with. Now that figure above it, "Efficiency" suggest that for ever watt it consumes, it produces 1.25 watts of heat. Granted that better than gas boiler, but that's actually concerning. That drastically changes my perception of what I'll get in terms of its performance, running costs and ROI.

interesting - but no fun if you've got a car you need to charge overnight Shame, ive lots of battery capacity for this, i just wished i worked from home more and did less miles!

So, within permitted development, I can install as many noisy non inverter air con units on my outside wall for the luxury of a cool room. But if I want to install a single heat pump to reduce bills and do some good, I need super quiet unit installed with a hefty MCS markup?

I've test been running with a flow temperature between 45 and 50 degrees for a few months now, so i expect not to have to change any emitters, and we run the heating 18 hours a day modulated by the tado thermostats in a fairly decently insulated home. Before anyone jumps in re the hot water, thats handled by the water heater seperately So yes we get a burst at 4 or 5am when it starts up, but that accounts for the 6 hours its been off. We're not the type to turn it on when cold and off when hot. Its left active spring to autumn and will silently keep temperature to within 0.2 degrees of where we want it By all accounts were doing well with it, apart from that ensuite above the garage So my assumption is that if we use 84 "units of heat" per day when on gas heating and its -10 outside, we'll require 84 "units of heat" from the ashp unit. so divide that by 24 and we arrive at 3.5 required every hour So, if the maths reckons 5.3kw then theres a definite inflation going on. However, i dont think i'm going to chance it with a 5kw unit, 8kw seems more prudent

(theres no hot water in the calculation or the gas usage as thats on a seperate standalone water heat pump.) i believe am comparing correctly. the google sheet shows me what the house (possibly) loses in one hour, 5kw, on the coldest day the gas usage is what is used to correct that heat loss in 24 hours, 83kw, including inefficiences, on the coldest day when we had -10° so 83 kw divided by 24 gives me 3.45kw per hour does it not.

Do you think the heater element is binary, on/off or is it modulated by an inverter as would seem sensible

I've been looking at a heat pump and sizing it based on the actual gas used to heat my house. Am i being stupid and this is real world data irrelevant as suggested by the heat loss calculator floating around? I've filled out as best i can, and over estimated the dreaded over-garage ensuite thats built to air change standards from the mid 16th century, not sure why they bothered with the window, but i digress. Its suggesting i need 5.3Kw per hour every hour during the coldest times. My actual usage during the coldest days of 2022 were 83Kw/day, or 3.45Kw/h If most installers are using the vastly rounding up figures before adding to the sheet, then overestimated figures on these sheets, then adding a pinch of salt and upgrading to the next bigger ASHP, i'd be on a totally unneccessary 12kw heat pump, whereas the 5kw unit, "flat out" would just about cut it.

Thats an acceptable compromise actually. thanks for the advice

Whilst thats an easy fix, thats most defintely my most unwanted results really. Im trying to save money and running a 3kw resistance heater for a week during subzero temps could cost me close to £30 per day at my current 40p peak rate I think i need to find one thats probably bivalent hybrid mode rather than one that switches itself off when its cold (LG Therma V) and switches in the 3rd party boiler

I'm looking at DIY fitting a heat pump at home. Rather than getting an oversized 12 or 14kwh ASHP to cover that one week a year when it drops to below zero, i wish to get a smaller unit that is properly sized to support the house 95% of the year and use the exisitng boiler as the stand in when things get really icy. A lot of the models from Mitsi, LG and others support this 3rd party boiler / Hybrid function and the logic sound good to me. However it begs the queston, what happens to the ASHP water loop when its really cold, the gas boiler is now running and the ASHP is offline for days on end. I know they run a defrost when the condensor coils freeze, and will run a cycle to keep the water circuit above 5 or 10 degrees if required. However looking at the LG THerma V units, the design prociple is to use a 3 way diverter to switch between the ASHP and the 3rd party boiler - so now its unable to run a defrost cycle, or receive water heated by the gas boiler as its out of circuit??

I'm not sure they can legally sell you that unit without seeing your F certificate. Throughout the rest of the world you can buy and self install, so it smells a bit like the required MCS install of solar panels and batteries racket i think. Simly hop over to mainland europe and pick up a Easy install DIY unit and bring it back.