Heat pumps, lock-down and darkest Somerset

[Hogboon]

The installer is MCS registered and room by room calcs were done - I assume by the same bloke who did the EPC so whether he got them right or not I don't know. The guarantee is 7 years. Ref. Larry's remarks about dirty electricity etc remind me of an excellent recent speech in the House of Commons [I know; I need to get out more...] by Jerome Mayhew Carbon debate HoC [whole speech is about ½ hour and v.g. and interesting i.m.h.o.]  in the course of which the boast last year by OFGEM [or whoever is 'in charge' of the grid] that UK grid gone 'carbon neutral' for the first time - albeit briefly - was achieved only by dint of topping up whatever was required from the grid by importing electricity from Holland. What was conveniently suppressed from the boast was the fact that this Dutch electricity was generated with - you guessed - coal! 

[SteamyTea]

19 minutes ago, Hogboon said:

Dutch electricity was generated with - you guessed - coal

Bit out of date

https://www.carbonfootprint.com/docs/2018_8_electricity_factors_august_2018_-_online_sources.pdf

[George]

It's all about trends, and the trend is a rapid decarbonising of the grid. 

 

Yes we'll be using fossil fuels for a while yet, but less and less every year.

[Rich123]

21 hours ago, George said:

I've got a 16kW Samsung ASHP and if anything I think it is oversized. The house heats up within a few hours so it doesn't run it continuously, which I believed was the most efficient way in winter. COP seems pretty good at 2.89 during the latest cold weather inc defrost cycles.

 

However, previously we had an one room oil rayburn and log burners so have nothing to compare it to.

 

When installed we did insulate and it was a complete new CH so rads are sized correctly. We also kept the 2No wood burners as supplementary heating - which when working from means I'm not using electricity to heat the office. 

Hi it’s interesting about the heat pumps, provided that yours is fully inverter controlled,then over sizing is actually probably more efficient as the heat transfer through the exchanger is more efficient. A  COP of near 3 is good for ASHP. I’d be interested to know what the annual COP is if that’s a winter figure.

[George]

On 09/01/2021 at 08:30, Rich123 said:

Hi it’s interesting about the heat pumps, provided that yours is fully inverter controlled,then over sizing is actually probably more efficient as the heat transfer through the exchanger is more efficient. A  COP of near 3 is good for ASHP. I’d be interested to know what the annual COP is if that’s a winter figure.

 

Oh that's good to know - it's a Gen6 Samsung EHS so it is bang up to date and I hear it ramping up and down so the inverter control is doing something. 

 

I'll certainly keep tracking COP - only have the on board generation calculation to go on, and the secondary energy meter to check against for usage.

 

 

[Ferdinand]

Somewhere in Peru there is a series of books about a Bear exiled from Somerset....

[SteamyTea]

1 minute ago, Ferdinand said:

Somewhere in Peru there is a series of books about a Bear exiled from Somerset....

Who drinks cyder with cheese sandwiches, rather than has marmalade ones.

[Ultima357]

On 12/01/2021 at 11:12, George said:

 

Oh that's good to know - it's a Gen6 Samsung EHS so it is bang up to date and I hear it ramping up and down so the inverter control is doing something. 

 

I'll certainly keep tracking COP - only have the on board generation calculation to go on, and the secondary energy meter to check against for usage.

 

 

Hi George. I too have a Gen6 Samsung in my new build property. Interesting to see your COP figures as mine just gives out fantasy figures, seemingly thinking that it is running at circa COP 20! This from the control panel. As for over sizing, they run most effectively at lower outputs I believe but may be wrong. I'm currently chasing Samsung on the issue of the anti freeze cycle. Mine wants to take it out of the hot water cylinder instead of the buffer tank, reducing the water temperature by 10 deg overnight in the recent cold weather. So I fitted a bypass switch to take the HW valve out of circuit (I switch it manually). As a passive build, just setting the overnight temps back a degree or 2 means it doesn't run otherwise overnight as we very little heat loss. 12kw model in 253m2. 

Edited January 19, 2021 by Ultima357
Clarification

[pdf27]

On 12/01/2021 at 12:26, Ferdinand said:

Somewhere in Peru there is a series of books about a Bear exiled from Somerset....

A guy I used to know now lives in Vietnam, teaching the locals English with a strong West Country accent. I really want to meet some of his pupils one day!

[Chris Bottomley]

Hi Hogboon,

We have a similar set up to you, also in Somerset- a 1960's large detached 4 bed chalet bungalow of 173m2 floor area insulated as well as possible for a house of that age. The EPC space heating requirement 16750kWh and 3500kWh for water heating.  Heating and hot water was supplied by a 28kW oil boiler feeding 13 radiators mainly single panel of 1970's vintage and a 12m2 underfloor heating loop in a sun room.

 

The oil boiler was replaced by a 12kW LG ThermaV Monobloc ASHP system in May 2020 based on a heat loss survey, most of the radiators were upgraded as part of the installation. Controls are the LG remote control unit and a single programmable thermostat.  The underfloor heating loop runs of the main heating loop as a separate zone under control of a second thermostat.  An MMSP monitoring system was fitted but unfortunately the installer didn't get their act together to enable us to get the additional RHI payment.  The monitoring has been useful however in allowing us to work out what the system is doing and when.

 

The ASHP performs well in terms of keeping the house warm although it is best not to vary the set temperature greatly during the day as the ASHP takes around an hour or so to raise the house temperature by a degree dependant on the flow temperature and outside temperature settings.

 

[Hogboon]

Apologies for opening old sores as it were; I had hoped to be back in triumph long before this. As nothing seemed to be happening apart from the weather getting a few degrees colder I gave the installer a nudge to remind him that round here all the brass monkeys lack cojones.  

According to them [the installer rather than the brass monkeys], having initially proposed replacing the existing LG Therma V 9kw heatpump with something larger, they were told or came to the conclusion themselves that this would not solve the problem. The explanation they gave me was something to do with ‘modulation’ along with more hot air than the heatpump currently seems capable of producing. There was even a suggestion of using the immersion heater in some way to ‘boost output’ but I stamped on that immediately. [I am waiting to hear if this was LG's bright idea.]

As things stand at present therefore the installer is reverting to plan A; i.e. replace current 9kw with something bigger. All of which has given me time to think and ask a few questions. Here are two.

1.   I have yet to hear a good word spoken about LG apart from those of the installer – not that I have heard particularly bad things about LG from others; as one man put it yesterday “they are all pretty reliable but…” and went on to say that in his opinion [he's CEO of an advisory group for heating engineers] LG were at the lower end regarding quality, performance, reliability etc. I have no axe to grind here and wonder whether this is an opinion shared by frequenters of this forum. By the same token one name seems to recur as first choice and that is Vaillant. Does anyone have a view on that? They seem to use propane as the refrigerant. 

2.   What exactly is the difference in performance between say any 7kw heatpump and a 14kw heatpump? Presumably a 14kw does not extract twice as much heat from a given volume of air as a 7kw heatpump?  but does a 14kw handle twice the volume of air in a given time as a 7kw thereby extracting twice as much heat in a given time? Or is it simply that a 14kw heatpump has a larger compressor, fan and pump and requires twice as much energy to operate as a 7kw heatpump? Or is the difference something else?

Thanks for your patience - meanwhile I am ordering more logs!      

[jack]

11 minutes ago, Hogboon said:

but does a 14kw handle twice the volume of air in a given time as a 7kw thereby extracting twice as much heat in a given time? Or is it simply that a 14kw heatpump has a larger compressor, fan and pump and requires twice as much energy to operate as a 7kw heatpump? 

 

It's both of these. You could presumably tweak some of these factors one way or the other and balance that out by changing one or more of the others, but in essence you roughly double everything.

[scottishjohn]

27 minutes ago, Hogboon said:

What exactly is the difference in performance between say any 7kw heatpump and a 14kw heatpump? Presumably a 14kw does not extract twice as much heat from a given volume of air as a 7kw heatpump?  but does a 14kw handle twice the volume of air in a given time as a 7kw thereby extracting twice as much heat in a given time? Or is it simply that a 14kw heatpump has a larger compressor, fan and pump and requires twice as much energy to operate as a 7kw heatpump? Or is the difference something else?

 

Thanks for your patience - meanwhile I am ordering more logs!      

yes  it just moves more air to get the bigger output 

I have a mitsubishi one a t8kw 

the 14kw has an outside box alot bigger and 2 fan units  instead of one-it just extracts heat from a larger volume of air

 do you have 3 phase?

it would be cheaper running on that i think

Edited February 11, 2021 by scottishjohn

[TonyT]

Can a larger heat pump modulate down to a lower rating? Similar To modern condensing boilers?

 

 

[George]

Just now, TonyT said:

Can a larger heat pump modulate down to a lower rating? Similar To modern condensing boilers?

 

 

 

An invertor driven one can, yes. The pump runs as hard (and draws as much energy) as is needed.

[SteamyTea]

Rather than think in volumes of air and air flow speed, think in terms of air mass and specific heat capacity.

All the theory falls into place then.

 

A larger unit may be more efficient overall.

Edited February 11, 2021 by SteamyTea

[AliG]

I just checked this as I had noticed when looking at heat pumps that some of them see a notable drop in output as they get away from ideal conditions. You have to be careful of this as non ideal conditions are often when you need them most.

 

After a lot of work on Google I found the full specs of LG heat pumps. It seems to me that they suffer from this issue more than others I have looked at.

 

The figure isn't given here, but with a flow temp above 35C and an outside temp below 2C it would seem likely that its max output drops to less than 5kW which would indeed make it undersized. Notice that with a 55C flow temp, the max output of the 5, 7 and 9kW pumps is actually the same!

 

 

 

[jack]

3 hours ago, George said:

An invertor driven one can, yes. The pump runs as hard (and draws as much energy) as is needed.

 

Larger pumps typically have a higher minimum output though, I believe. This can be an issue in a highly insulated house with an oversized heat pump, because the minimum output might be higher than is desirable.

 

16 minutes ago, AliG said:

I just checked this as I had noticed when looking at heat pumps that some of them see a notable drop in output as they get away from ideal conditions. You have to be careful of this as non ideal conditions are often when you need them most.

 

By way of comparison, I ran some figures a few years back when comparing a nominally 8kW unit against a nominally 5kW unit from a different manufacturer:

 

 

At the conditions the ASHP would experience most of the time where I live, the 5kW unit had a comparable output at worst.

 

No idea why the Nibe 2040-8 is considered an 8kW unit given it doesn't seem to ever output 8kW. Maybe there's some specific combination of exterior temps and production temps where it peaks at 8kW capacity?

[ProDave]

As many of you will be aware I am the owner of an LG heat pump, and older model 5kW version.  I had some teething problems that have been well documented on here and largely solved by myself.  I found their technical support to be wanting.  I am loathed to criticise them however as knowing mine is an old unit I would hope the issues I had have been corrected on more recent versions and seeing as you don't hear lots of complaints about the issues I had that is probably the case.

 

We were down to -14 last night, and my LG ASHP has been working without issue keeping the house warm and heating the DHW.  We have reached a daytime high of -4 just now.  I would be surprised if many of you have a lower outside temperature than here (unless you live near Braemar which reached -22.9 last night, a record low for the UK this century)

 

If you want to experience worse, feel for a friend who installed an good energy ASHP last year, and it stopped working last night with an error message that meant "ambient temperature too low"  I have not heard yet how he has got on speaking to the manufacturer about that issue.

[Hogboon]

 

17 hours ago, ProDave said:

We were down to -14 last night, and my LG ASHP has been working without issue keeping the house warm and heating the DHW.  We have reached a daytime high of -4 just now.  I would be surprised if many of you have a lower outside temperature than here (unless you live near Braemar which reached -22.9 last night, a record low for the UK this century)

 

If you want to experience worse, feel for a friend who installed an good energy ASHP last year, and it stopped working last night with an error message that meant "ambient temperature too low"  I have not heard yet how he has got on speaking to the manufacturer about that issue.

 

-23º ? What are they whingeing about? Tell them to get an LG Therma V. LG's website [still] claims:

 

Quote

"It can operate even at extremely cold weather like -25°C. Moreover, it can offer leaving water temperature of 65°C"

 

which just goes to show what a keen sense of humour the Koreans have. 

[scottishjohn]

5 minutes ago, Hogboon said:

 

 

-23º ? What are they whingeing about? Tell them to get an LG Therma V. LG's website [still] claims:

 

 

which just goes to show what a keen sense of humour the Koreans have. 

I bet it don,t say its  COP ratio of 3 at that temp 

will be cop of 1 or less if it can work that low  outside temp

 maybe got an immersion heater in line to lift temp of output if heat pump cannot keep up

Edited February 12, 2021 by scottishjohn

[pdf27]

3 minutes ago, scottishjohn said:

I bet it don,t say its  COP ratio of 3 at that temp 

will be cop of 1 or less if it can work that low  outside temp

 maybe got an immersion heater in line to lift temp of output if heat pump cannot keep up

If it has a COP of less than 1, where is the rest of the heat going?

[SteamyTea]

2 minutes ago, pdf27 said:

If it has a COP of less than 1, where is the rest of the heat going?

Pumps and parasitic loads.

[scottishjohn]

1 minute ago, pdf27 said:

If it has a COP of less than 1, where is the rest of the heat going?

power consumption to run the unit against actual heat recovery from the cold air

everything takes power to run and COP is measure of kw power IN  to  KW heat OUT

[scottishjohn]

If we got -15c to -23c regularly every year in uk for long periods  --then thats when GSP would be a better choice-