@ianjrw 

I wish I could get actual energy usage for our ASHP, but my MMSP has never worked properly.  Installers have been back to try and resolve it, but failed miserably.  I just don't trust any of the figures I get from it, e.g. for the hour from 0500 to 0600 it is telling me that our ASHP consumed 4kwh, and generated approx 3600kwh with a CoP of about 900!  Generated figure is obviously wrong, and I don't believe the consumed figure either.  The consumption meter for our ASHP is mounted within the unit itself, so in order to get accurate figures I would have to take the cover off every day.  I only really have whole house consumption figures to go on, and there are so many variables there that it is not worth the effort to even try.

@peterr nice COP! Ta, know what u mean - we havent got our monitoring app yet so unsure what usage is for heating\HW. And trying to compare usage of previous heating solution (electric boiler) vs none-heating-usage is pretty useless/lots of effort...especially as we have econ 10 tariff...and @derek-m truth point about no two days being the same...case of try & test, i think! 

@alec-morrow 

I don't disagree with anything that you have written in your posts above.

Part of the problem, certainly in our case, and no doubt in quite a few others, is that our installer had no interest in making the system work properly.  They just wanted to get the install done and get the system "working" (i.e. generating heat) in as short a time as possible.  The support I have received from them in trying to get our system running more economically has been woeful, I think, in part, because they don't actually understand how to do it themselves.

With the technology available today, it really should not be difficult to get almost every heating system in the country working much more efficiently, but nobody in power wants to spend the money, in spite of the obvious advantages it would bring, and the average homeowner isn't interested, although peoples attitudes will hopefully change with ever increasing energy prices.

Even though our house is only 15 years old, the building fabric was never designed with energy performance in mind - quite a few large south facing windows and a construction methodology that is proving very difficult to draught proof, although I am getting there slowly.  I haven't looked into MVHR much, but I think it would probably be very difficult to retrofit to our house.  I am starting to think we would be better selling up, buying a piece of land and building our own Passive House!

Thanks all - really insightful/educational chat. Since install on 14th the house has been very happy on weather comp of 38@-3 25@15. I'll see how that copes over next few days! Also check with the installers if i can drop a room stat in/out by just using the controller unit alone so I can test a week or so with the stat at +2C above our standard vs not using it at all. 

Posted by: @ianjrw

Thanks all - really insightful/educational chat. Since install on 14th the house has been very happy on weather comp of 38@-3 25@15. I'll see how that copes over next few days! Also check with the installers if i can drop a room stat in/out by just using the controller unit alone so I can test a week or so with the stat at +2C above our standard vs not using it at all. 

I just set my stats to 30 degrees if I want to take them out the loop.  That way they are always calling for heat leaving weather compensation to do its thing. 

Posted by: @kev-m

Posted by: @alec-morrow

@kev-m 

 

Raising a heat curve will always use more energy. But if you turn off with on off controls you will need more energy at the start if a phase change.

Mixing and matching on off controls with compensation controls is fraught with frustration.

Using a weather station which looks at wind and solar gain from a sensor, that’s the way they do it in more advanced countries..that uses a feed back signal to vary flow 

Imagine if heating systems had the same sensors, controls, automation and efficiency of modern cars.  Things would be very different.  If cars were like heating we'd still be driving a 1970 Ford Escort with points and a manual choke.   

 

they do, or at least they can do.

i install multi sensor systems on gas boilers and they are both good and reliable. one client added 120m2 of floor to a 400m2 house and incurred no significant extra  energy cost. Designed in Germany and installed as in Germany…pays huge dividends 

Posted by: @alec-morrow

Raising a heat curve will always use more energy. But if you turn off with on off controls you will need more energy at the start if a phase change.

Mixing and matching on off controls with compensation controls is fraught with frustration.

In general, yes to all of the above. In particular, with a Mitsubishi ecodan, no, raising part of the curve does not always use more energy, because they have a relatively high minimum output, which means it is sometimes better to stop for a while and restart later than have it on at a low output with it cycling. Crudely, the start-up seems to use roughly double the energy until the flow is back up to target, so you save money if you stop for longer than the time that takes your system.

• @mjr indeed. heating a room is a zero sum game..but that’s well down a steep learning curve for many.

the main thing is to always use compensation controls indoors as well as the outdoor sensor

Never use controls from third party manufacturers

@alec-morrow I can't completely agree with that. The Mitsubishi FTC6 is simply not smart enough yet for all homes. I'm not here to make the fine adjustments based on the weather and forecasts, so heating cost more before I added a third-party programmable controller (using EmonCMS and Node-RED) to the mix. The only mode the FTC6 has which uses the indoor sensor is the Auto Adaptation mode described in this discussion, which ignores our lovingly crafted weather compensation curves and seems far too aggressive in ramping up the flow temperatures.

So I feel that third-party controllers are almost essential for economic ecodan use, but make sure they are really compatible with your heatpump and not just a dumb on-off switch or signal!

Not sure where to post this but here goes.

I am thinking that a A2A HP behaves differently from a A2W overall

The A2W seems to be always dictated to by some control somewhere and therefore can be operating a little off max efficiency.

The A2A seems to just do its own thing and operate at conditions which suit it and therefore achieves higher cops.

I want a HP which behaves like my swimming pool A2W one in that it takes water in and emits it at 1C higher seemingly for ever.  ie heat the water or air by a optimum for COP not by any other parameter. If that leaves the room/house too cold or hot so be it as i will let the thermal mass of the house deal with it at least up to say 25C

What do you think.

@mjr im sorry I missed this.

but yes if you can’t be bothered to fine tune on off controls will crudely solve the issue, at a price of higher energy usage!

@kenb no they dont.

contol technology just expects the flow temp to rise if the room isn’t at set point, and to wind down if it’s over set point.

If your pool is not rising in temperature and you are happy I wouldn’t really worry about the rest.

I do see people happy with systems they don’t understand giving them selves mental grief over things that don’t matter (ie is why is my room warm but radiator cool)