Heat pumps

QrizB

matt_drummer said:

This is the other thing, when it's a bit cold, it doesn't always have to be that cold, it spends 30% of it's time defrosting, so not producing any heat.

Just to mention, it'll need to defrost less when it's properly cold rather than just a bit cold.

At 2C the vapour density of water is about 5.7g per cubic metre of air. At -2C it's only 4.4g, and at -5C it's 3.6g. This means there's less water in the air to form ice on your evaporator.

matt_drummer

QrizB said:

matt_drummer said:

This is the other thing, when it's a bit cold, it doesn't always have to be that cold, it spends 30% of it's time defrosting, so not producing any heat.

Just to mention, it'll need to defrost less when it's properly cold rather than just a bit cold.

At 2C the vapour density of water is about 5.7g per cubic metre of air. At -2C it's only 4.4g, and at -5C it's 3.6g. This means there's less water in the air to form ice on your evaporator.

That is very true.

Daikin heat pumps seem to have a very cautious approach to the possibility of ice build up. Mine seems no different to the others I know about, it defrosts even when it's 7+c outside and not the slightest sign of ice.

As far as I understand, although I may be wrong, it is because they cut corners/costs and don't install enough sensors to detect ice build up. Defrosting occurs when certain conditions at the sensors they did fit are met, whether there is ice or not.

Sometimes when I am watching the data you can see it building up to a defrost, there are subtle changes in the  heat production, you can `feel' the defrost coming.

It's annoying.

When it was properly defrosting it would heat for about 23 minutes at most and then defrost for 10 minutes.

I have seen -3c or so with it and the defrost is as bad as +2c.

I would expect it to go away at colder temperatures but I haven't seen it yet.

matelodave

I know you want to get maximum performance out of your heatpump but TBH you do seem to be worrying yourself into an early grave

matt_drummer

matelodave said:

I know you want to get maximum performance out of your heatpump but TBH you do seem to be worrying yourself into an early grave

It's a fair comment.

I could just leave it as installed and try to improve it over time.

I have chosen to sort it out properly as quickly as I can so I can forget it and move on to something else.

The whole thing was a personal challenge to see if I could make it work, run off solar and never buy energy again.

It's probably not how you think though. There's little help from the manufacturer or installer so I find the easiest way is to gather as much input from other people as I can. I get quite intense about it but I found it gets the answers quickly, I could do it more gently but it just prolongs the process and I am already bored of it.

It is now running quite well though.

I won't be ill over it, it heats the house and I can afford to run it, none of it is the end of the world although I know I make it sound like it at times.

matelodave

Actually it is how I think.

When I had ours fitted some 13 years ago I had a multichannel data logger measuring room temps, flow and return temps outside temps and an energy monitor to try an correlate them all together and it took me the whole of the first winter (which was exceedingly cold) to try and set it all up.

What I did find however was that excessive zoning not only reduced comfort because room temps dropped overnight and so took ages to recover but it also reduced efficiency because it made the heapump cycle a lot more often when the stats clicked in and out and closed off the floor loops.

So we now have all the room stats set to a degree or so above the desired room temp and have tweaked the weather compensation and flow temps through the floor loops to keep the rooms a bit below the stat settings. The heatpump flow temp reduces overnight rather than being shut down completely and so the place doesn't  cool right down.

My wife now doesn't complain about being cold even though the room temps are generally only around 19 degrees during the day and 17 overnight.

Our worst year energy wise was the year we installed it and got through 8600kwh (but thats for all our electricity) we've got to an average of about 7200kwh (actually 7013 over the past 12 months)

I wouldn't say that we've got it tweaked to perfection but we have as much hot water as wee ned when we need it and we aren't cold at anytime during the day or night. We are pretty bad at shutting off rooms that are not in use but TBH the only room that doesn't get used during the day is our bedroom, the others are used one as a study and the other although the spare bedroom has my 3D printers in it which get used frequently. I reckon 50% of our consumption is day-to day (including hot water) and 50% is heating

Netexporter

Has anyone got any experience of Ideal heat pumps? I have to confess I didn't know they made them, until today, although I did have one of their boilers at my previous gaff.

mrmmhf

Just came across this regarding cheaper made in China heat pumps: 

https://renewableheatinghub.co.uk/have-consumers-been-lied-to-about-the-efficiency-of-heat-pumps-made-in-china

QrizB

mrmmhf said:

Just came across this regarding cheaper made in China heat pumps: 

https://renewableheatinghub.co.uk/have-consumers-been-lied-to-about-the-efficiency-of-heat-pumps-made-in-china

Per a seemingly well-informed comment on RHH's forum, the Chinese OEM manufactuers are quite up-front about the performance of their heat pumps. It's the European VARs that are inflating the values.

The example quotedn their forum compares the Chofu OEM data to the "well-known UK stockist" performance claims.

The stockist can be found by web searching the quoted product codes ...

Reed_Richards

It's well known that Grant heat pumps are rebadged Chofu ones.  I haven't searched to see if this is what is being referred to.

oliver1951

matt_drummer said:

matelodave said:

I know you want to get maximum performance out of your heatpump but TBH you do seem to be worrying yourself into an early grave

It's a fair comment.

I could just leave it as installed and try to improve it over time.

I have chosen to sort it out properly as quickly as I can so I can forget it and move on to something else.

The whole thing was a personal challenge to see if I could make it work, run off solar and never buy energy again.

It's probably not how you think though. There's little help from the manufacturer or installer so I find the easiest way is to gather as much input from other people as I can. I get quite intense about it but I found it gets the answers quickly, I could do it more gently but it just prolongs the process and I am already bored of it.

It is now running quite well though.

I won't be ill over it, it heats the house and I can afford to run it, none of it is the end of the world although I know I make it sound like it at times.

Hi Matt, how are things going now. I think you changes the heat pump to the 8kw?