Heat Pumps

[djenson]

I suspect that sort of radiator is a fan assisted type

Sure is.

 

[emmrecs]

@Rolfe

Slightly OT but I see your favourite Green politician is "on the warpath" again.

Removing Scottish Government subsidies for those installing Solar PV and Batteries

But, of course, those of us "south of the border" have not enjoyed such benefits!

 

[BarryH]

I've had a full and I mean full room by room heat-loss survey done on my house so I won't have some salesman (no offence I used to be one) try to pull the wool over my eyes and the upshot is that my house fitted with an 18 kW gas boiler has a 4.7 kW heat loss with -2C outside and +20C inside. It would be recommended to install a 6 to 8 kW ASHP according to Mitsubishi recommendations to have the capacity to also heat a 250-litre hot water cylinder. I would expect with some upsizing of some radiators and downsizing of 2 of them to achieve a SCOP of almost 4 and a COP of 5. Given I have Solar Panels, a Home Battery and a tariff with 6 hours of electricity at 7.5p throughout the night I think the running costs would be significantly lower than sticking with gas boiler.

By-the-way, Octopus is currently offering additional discounts on ASHP supply and fitting at the moment. with all-inclusive Fixed Price of £3,000 for a "Standard" home and homes that are more complex and have a poor EPC will have a higher but still fixed price.

 

[tsedge]

I've had a full and I mean full room by room heat-loss survey done on my house so I won't have some salesman (no offence I used to be one) try to pull the wool over my eyes and the upshot is that my house fitted with an 18 kW gas boiler has a 4.7 kW heat loss with -2C outside and +20C inside. It would be recommended to install a 6 to 8 kW ASHP according to Mitsubishi recommendations to have the capacity to also heat a 250-litre hot water cylinder. I would expect with some upsizing of some radiators and downsizing of 2 of them to achieve a SCOP of almost 4 and a COP of 5. Given I have Solar Panels, a Home Battery and a tariff with 6 hours of electricity at 7.5p throughout the night I think the running costs would be significantly lower than sticking with gas boiler.

By-the-way, Octopus is currently offering additional discounts on ASHP supply and fitting at the moment. with all-inclusive Fixed Price of £3,000 for a "Standard" home and homes that are more complex and have a poor EPC will have a higher but still fixed price.

Roughly what will your total spend be if you do this? (from your current setup, not from scratch).

 

[BarryH]

Roughly what will your total spend be if you do this? (from your current setup, not from scratch).

I had a Quote for £14k from I forget who now because there was no way I was paying that last year and in January the provisional from Octopus was around £10-11k for 11/14 kW ASHP after the full 3-hour survey and heat loss calculation. Last week another reputable provider (the one who did the independent paid up front 3-hour survey) suggested a Mitsubishi 8.5 kWh ASHP with additional radiators c£10k.

I went back to Octopus because there had been talk of them subsidising ASHP roll-out and they quoted £6,800 based on my ECP data.

Unfortunately, my ECP is 8 years old and out of date as I've done a lot of work in the past 5 years since I've been here and significantly increasing insulation, replacing all windows and doors, replacing all lighting for low energy lighting, fitting 5 kWp of Solar and 10 kWh battery Storage and a low loss Heat Battery for domestic hot water. so I'm booking a new EPC this afternoon.

By The Way, The Survey was £300 plus Vat but if I went ahead with the provider who did the survey then this would be taken off the cost of the ASHP and the VAT refunded as the survey would have been the first stage of the project. I thought it worth spending the £300 + Vat for peace of mind I wasn't getting done over. You could do the work yourself with an App (make sure you use a proper paid-for App without strings attached for an honest reliable calculation and be sure it says that the algorithms used are BS compliant). The App will only cost about a fiver and test yourself to see if you've the stamina for it or would rather pay £300

 

[kin]

I just had a quote from Octopus to have ASHP installed for £560 all inclusive!

 

[johnb80]

I just had a quote from Octopus to have ASHP installed for £560 all inclusive!

Go for it, sounds perfect

 

[kin]

I used very little gas anyway, my annual gas usage is approx 5500kwh according to my gas bill. I use my gas to cook and take showers, most of house heating was provided by my aircon in bedroom and aircon in the lounge, thermostat is set at 16C for the whole house all year round.
From the few posts I’ve read so far, ASHP should be on 24/7? I’m currently on Intelligent Octopus at 7.5p off peak and 30p day, but octopus also offer Cozy Octopus but at 16p over night and a few hours during day, I’m wondering whether it would really save me any money.
Of course, I may change it for the environment and the sense of duty.., and my house is probably more saleable too!

Edit: I also have 10panels (4kw) solar and a 5kw battery.

 

[Gadget Geek]

I'd bite their hand off at that price.

 

[Gomev]

I used very little gas anyway, my annual gas usage is approx 5500kwh according to my gas bill. I use my gas to cook and take showers, most of house heating was provided by my aircon in bedroom and aircon in the lounge, thermostat is set at 16C for the whole house all year round.
From the few posts I’ve read so far, ASHP should be on 24/7? I’m currently on Intelligent Octopus at 7.5p off peak and 30p day, but octopus also offer Cozy Octopus but at 16p over night and a few hours during day, I’m wondering whether it would really save me any money.
Of course, I may change it for the environment and the sense of duty.., and my house is probably more saleable too!

Edit: I also have 10panels (4kw) solar and a 5kw battery.

Add to your battery capacity and run it off that during the day.

You may or may not have seen this.

 

[Exdro]

If it sounds too good to be true…..?

 

[kin]

Add to your battery capacity and run it off that during the day.

You may or may not have seen this.

He has 19kw battery storage, that’ll deffo work out for him through the winter, fully charged his batteries for £1.42 and leaving his car charging aside, he’ll never use 19kw in a day even with his heat pump at maximum for 24hours.
Even without his solar, I think he’ll still be a winner!

 

[BarryH]

I used very little gas anyway, my annual gas usage is approx 5500kwh according to my gas bill. I use my gas to cook and take showers, most of house heating was provided by my aircon in bedroom and aircon in the lounge, thermostat is set at 16C for the whole house all year round.
From the few posts I’ve read so far, ASHP should be on 24/7? I’m currently on Intelligent Octopus at 7.5p off peak and 30p day, but octopus also offer Cozy Octopus but at 16p over night and a few hours during day, I’m wondering whether it would really save me any money.
Of course, I may change it for the environment and the sense of duty.., and my house is probably more saleable too!

Edit: I also have 10panels (4kw) solar and a 5kw battery.

I know some people are scared of this 24/7 principle but check out Heat Geek on Youtube and you'll see why that principle works. It's a mind-shift just like it is when you move from ICE to EV where we have a shift in thinking of 5 minute forecourt stop with ICE to 6 hours overnight EV home charging. With Gas, the radiators run hot and you usually turn heating on during the day when you are home then off at night or when you are away from home this is actually inefficient just like driving an ICE car accelerating and braking all the time. ASHP on the other hand maintain heating in the home and keeps you comfortable at a lower cost by running radiators at a lower "radiator" temperature so, transfers the same amount of energy but over a longer time period. Rather than switching 'off' the just "set-back" the temperature is a few degrees and therefore the building fabric becomes a reserve of heat. Have you ever noticed how in the summer months you feel warmer in the evening when the room temperature is 20C than you do in the winter with the heating on at 20C? that's because in the summer the fabric of the home is warm whereas in winter the Gas heating is sucking up the heat when the heating comes on. So ASHP works with the building rather than fight against it.

The bottom line is 24/7 yes, but not at the same room stat temperature you're used to using with your gas boiler. And remember during the set-back hours the ASHP can be pumping heat into the hot water cylinder plus you can do all this hot water heating and overnight background heating at off-peak electrons just like your EV.

 

[johnb80]

Rather than switching 'off' the just "set-back" the temperature is a few degrees and therefore the building fabric becomes a reserve of heat. Have you ever noticed how in the summer months you feel warmer in the evening when the room temperature is 20C than you do in the winter with the heating on at 20C? that's because in the summer the fabric of the home is warm whereas in winter the Gas heating is sucking up the heat when the heating comes on.

Humidity is the greater feel of heat in the summer, when humidity is high everywhere feels warmer and for me uncomfortable. Put aircon on in the room with the same temperature but run it as a dehumidifier, the difference is amazing.

So ASHP works with the building rather than fight against it.

ASHP provides heated water, nothing more, nothing less, just the same as a gas / oil / solid fuel boiler does, sometimes at different temperature.

The bottom line is 24/7 yes, but not at the same room stat temperature you're used to using with your gas boiler. And remember during the set-back hours the ASHP can be pumping heat into the hot water cylinder plus you can do all this hot water heating and overnight background heating at off-peak electrons just like your EV.

A couple years ago I looked at getting an air-water heatpump installed, £15k was the quote and several radiators were to be replaced. I didnt go ahead and continued to use my gas boiler powered central heating along with air to air heatpumps in most rooms. Last December when we had a particularly cold spell and having read that most condensing boilers arent operated within their condensing range I thought it was time to do a trial. I lowered the flow temperature of the gas boiler down to 35 degC and left it on 24/7. I left the hot water to the immersion heater during off peak times. The net result was the house was perceivably warmer, radiators in most rooms were operating their radstats i.e. turning the flow down and we used less gas. The boiler efficiency roughly measured in Home assistant went up from 61% to 89%. The above trial gave me the confidence to buy an air water heatpump, install it myself and no need to change the rads. Instead of spending just over £15k, I've spent less than £3K installing a second hand Mitsubishi Ecodan unit (14 kW).

J

 

[BarryH]

Humidity is the greater feel of heat in the summer, when humidity is high everywhere feels warmer and for me uncomfortable. Put aircon on in the room with the same temperature but run it as a dehumidifier, the difference is amazing.


ASHP provides heated water, nothing more, nothing less, just the same as a gas / oil / solid fuel boiler does, sometimes at different temperature.


A couple years ago I looked at getting an air-water heatpump installed, £15k was the quote and several radiators were to be replaced. I didnt go ahead and continued to use my gas boiler powered central heating along with air to air heatpumps in most rooms. Last December when we had a particularly cold spell and having read that most condensing boilers arent operated within their condensing range I thought it was time to do a trial. I lowered the flow temperature of the gas boiler down to 35 degC and left it on 24/7. I left the hot water to the immersion heater during off peak times. The net result was the house was perceivably warmer, radiators in most rooms were operating their radstats i.e. turning the flow down and we used less gas. The boiler efficiency roughly measured in Home assistant went up from 61% to 89%. The above trial gave me the confidence to buy an air water heatpump, install it myself and no need to change the rads. Instead of spending just over £15k, I've spent less than £3K installing a second hand Mitsubishi Ecodan unit (14 kW).

J

Thanks for that feedback John. I did a similar experiment with my condensing gas boiler last winter. I don't have any inbult means of temperature reading the flow and return of my Worcester boiler and so I fixed the sensors of two inexpensive digital thermometers to the flow and return pipes as they go into and leave the boiler. I had ensured that these 2 devices read within ½ Degree as a calibration exercise. Once fixed I lagged them with good foam pipe insulating sleeves. I then adjusted the boiler down in stages until the Return to the boiler was below 50 and the HIVE main room stat I set to 19C during the Day and set back to 17C overnight. the HIVE App showed me the rate of cooling overnight and only once or twice on the coldest days last December did the boiler fire up overnight when the temperature dipped below 17C. At first, the "Delta T" at the boiler between the Flow and return was 11C meaning at this lower temperature the radiators were not emitting, or releasing, enough of the heat carried by the water into the room I next went all around the house opening all the radiator's thermostatic valves (TRVs) to maximum number 5 to ensure as much radiator area was warm and radiating heat into the house. One or two rooms were oversized and once things had stabilised I adjusted the other valve on the radiator (the locksheild valve) to balance the system the left things a loan. The only tweak after this was to set the main HIVE thermostat in the lounge up 1 degree C in the evening from 7 p.m. to 10 p.m.

Hot Water I heated overnight by electricity on Go even though last winter the rate per kWh was slightly more on Go than the kWh of Gas. Why well it is down to efficiency. Firstly I'd had to raise the boiler flow to over 60C to heat the water effectively and that would have made the heating less efficient. And secondly, I had already established that I was using 9 kWh of gas on average just for hot water whereas heating the water electrically I used only 5 to 5.5 kWh a day. Electrical heating is 100% efficient whereas Gas has many inefficiencies in heating domestic hot water because a boiler needs to fire up to a higher flow temperature than the water in the cylinder and since there is only a small amount of water in the boiler, pipes to the cylinder and the coil heat exchanger in the cylinder the return to the boiler is too hot for condensing action in the boiler which then shuts the burner down and the pattern repeats. This is called cycling and is very inefficient.

Oh, and I should say that the experience last year convinced me that a heat pump would work. However, the house could have been a little more comfortable with larger radiators in the lounge in particular which has been born out by the two independent Heat Loss surveys I have had done by Octopus and an independent HeatGeek surveyor since last winter, but that is another story!

Two quick and dirty methods to get to the heat pump size you need are: Find out how many kWh of gas you used on the coldest day last year and divide by the number of hours you want to have at the Comfort temperature say 16 hours and 8 hours at setback. So for me 120 kWh/ 16 hours + 7.5 kW Heat Pump for worst case day. The other is to use the Gas used the past 12 months and divide by 2700 and allow a little more for water heating. So for me, I used 13,000 kWh/2700 = 4,8 kW a 5+ kW Heat pump will do me for an average day heating. Taking into account my building type the professionals say to provide flexibility when a cold day follows a warm day I should actually install an 8 or 9 kW Heat pump.

To get your combi to condense and become more efficient you need temperatures down around and below 50/55 degrees return water temperature as you can see from the graph above.

Thanks to for the above graph to Heat Geek as it was lifted from this excellent article by Heat Geek.

Condensing Theory: How Do Condensing Boilers Add Efficiency

 

[Gadget Geek]

I had a Tepeo Development Manager and a heating engineer come to my house yesterday to do a survey for a Zero Emmission Boiler (ZEB). Everything went well and I'm just waiting for the quote for the ZEB + installation. They said it will be no more than £6,000, and probably a lot less due to the position of the existing gas boiler and immersion tank. I'll keep you posted.

 

[Rayz]

I would honestly hold back , Do more research on the time it takes for what for 3 bed property to get to temp. It's a very slow process to get to temp. But yes it is hell of a lot cheaper to run. My first experience of first buying a heat pump tumble dryer a few years ago. Again it takes double the time to dry, but save over 50%running cost. I looked into a heat pump for central heating after much research and speaking to people. Fifty percent regretted getting one cos of slow process heating the property. I'm keeping an eye on the valiant heat pump. They may be expensive but have a lot of experience of heating appliances.

 

[Gadget Geek]

I would honestly hold back , Do more research on the time it takes for what for 3 bed property to get to temp. It's a very slow process to get to temp. But yes it is hell of a lot cheaper to run. My first experience of first buying a heat pump tumble dryer a few years ago. Again it takes double the time to dry, but save over 50%running cost. I looked into a heat pump for central heating after much research and speaking to people. Fifty percent regretted getting one cos of slow process heating the property. I'm keeping an eye on the valiant heat pump. They may be expensive but have a lot of experience of heating appliances.

This isn't a heat pump, it's a heat battery.

Any electricians out there who can advise please?

I've been given a quote of £660 to upgrade my consumer unit to; 18th edition Amd2 type A RCBO board and surge protection. Does that price sound right?

 

[siteguru]

Are they replacing all the breakers / supplying new ones? How many circuits? Is it all one unit, or is there a separate CU for the EVSE for your car?

(A photo of your existing CU might help people to visualise what's to be done).

 

[Gadget Geek]

Are they replacing all the breakers / supplying new ones? How many circuits? Is it all one unit, or is there a separate CU for the EVSE for your car?

(A photo of your existing CU might help people to visualise what's to be done).

None of the above. It's to replace one of these;