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I’ve just started my investigation into air-source heat pumps and home battery storage.
So far I’ve concluded that my house could run on a pump without much in the way of radiator replacement and I’ve also enquired about a hybrid heat pump which allows the gas combo boiler to stay to top up the air source heat pump in very cold days. It also will continue to supply me with hot water rather than installing a tank.
The battery storage is causing me a few problems, I have been concentrating on getting a price for a Givenergy 13kwh all-in-one 6-battery and have had a price from an installer. I have since spoken to another installer who has stopped using Givenergy batteries due to the problems they have had with them. He suggested getting a Tesla Powerwall stating “they were far superior and would only cost about £500 more that the equivalent Givenergy battery.
I will be continuing getting prices and info but any input from you guys would be welcome.
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.
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160m2 would require a 8kW heatpump. If the home has poor building fabric insulation you would require one 1.5 times bigger. Similar applies, if you live further north where the outside temp is colder, requiring the system to work harder if not sized correctly,
As a rule of thumb you are looking at a heatpump somewhere between 9 to 11kW which would be capable of running the house.
However, I can’t stress enough how important it is to do a proper heat loss calculation, which will not only be more accurate but also calculate the internal temperature required against the outside temp in your area and the average number of heating days per year and come up with an accurate size for your requirements/needs, as an heatpump too small for the house will cause it to work harder and fail prematurely. A system that is too large will cause the system to cycle.
For what its worth a 5kW system would be suitable for the averaged sized 3 bed house, upto 100sqm.
@kezo I misread his info this is what he actually said. I just went to the price he quoted and glanced at the rest ?
“Please see estimate attached for a Vaillant ASHP supply and install and your estimated heat loss report. 10.61kW “
“I recommend a 12kW Arotherm plus.”
This is where I get lost, if I use 16,500 kWh of gas per year, how does the stated heat loss relate to that?
Is the heat loss a value of the heat I am losing on a daily basis?
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.Also, the ASHP in my situation will have the backup of the combi boiler in really cold conditions and the temp at which this clicks in can be changed. So it can be set to say +7 or -2 *C as the start-up temperature. A bit of trial and error would decide the best temp to set it at.
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.I found this online.
Heat loss represents the energy required to keep a room at a given temperature on the coldest days. It is typically measured in kilowatts (kW) or British Thermal Units (BTUs). A more technical definition for heat loss is the total transfer of heat through an object. It can occur through four main processes.
Four Types of Heat Loss
Whether the subject at hand is the human body, a building, or a mechanical component, there are four types of heat and thermal energy loss to be aware of:Convection: Convection occurs when heat is transferred from one surface to another through fluids — either gases or liquids.
Conduction: When heat travels through a solid material to whatever is outside of it via direct contact, this movement is called conduction.
Radiation: Electromagnetic radiation moves energy through air, though it is usually not seen. This type of thermal loss is not effective for ambient temperatures. The sun is one common example of electromagnetic radiation in nature.
Evaporation: Evaporation occurs when a fluid’s latent heat takes in the necessary energy to change into a gas.
If skin temperature is greater than that of the surroundings, the body can lose heat by radiation and conduction.So 10.61 kw is the heat loss from my entire house on the coldest of days?
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.@kezo I have been looking at the highest-output hybrid ASHP and Bosch does a 9kwh unit. This could be the best of both worlds for my particular install. I have a couple of installers coming soon so this is the unit I will be asking them to price on.
Kezo thanks very much for your time, and patience lol it’s been a learning experience and I certainly have a new found appreciation of electricians ?
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.Is the heat loss a value of the heat I am losing on a daily basis?
Yes you could say that, based on the coldest day.nigt of the year in relation to the internal temperature.
Heat loss is based on U values of the fabric the building and whether a room has an 1 or more outside walls, with or without a window and whether the remaining internal walls in the room face a heated room or not.
Simply the lower the heat loss, the less energy is needed to heat your home v the higher the heat loss more energy is needed to heat your home.
The basis of calulating heat loss is on a room by room basis and from this you come up with a total heat loss for the home, based on the outside temperature (worse case) and heat required indoors which can be calculated on temperature requirement for downstairs and upstairs or room by room basis.
Transmission losses is based on each component of the building fabric U value (walls, roofs door, windows) where we try to find out how much heat passes through.
Transmission heat loss (area x U Value x temperature difference)
Ventillation losses is based on the number of air changes a room has i.e replacing air inside with colder air outside.
(Volume x Air change rate x specific room heat capacity x temperature difference)
Thermal Bridging (Cold bridging) happens when part of the buiding envelope (external walls) allow heat to pass through more easily i.e you have an internal wall that joins the external wall without sufficient measures to prevent a thermal bridge. (you put your finger on ice cube & it zaps heat away from your finger lol)
Thermal bridging is added to the calculation through clculating the Y value (forget the calculation sorry)
The total heat loss is calculated by adding all these together.
MCS qualified installers, should be calculating the heat loss on a room by room basis. EN12831 compliant calculator is in a link provided yesterday if you want a play.
So 10.61 kw is the heat loss from my entire house on the coldest of days?
so he estimated!
This may help, although for CH the principle remains the same.
@kezo yes, he estimated based on the info I gave him over the phone but I suppose it gives some indication of the ball park I am in.
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.We went from oil so I can’t give you gas figures but we used roughly about 1000 litres of oil a year on average bad winter maybe more bit…. We’re in a well insulated 1930s 3 bed semi Radiators are 5 large double wall, 1 triple wall, 4 small single Our ASHP was either 5kw or 8kw can’t remember but definitely no larger. This perfectly keeps the house at 19/20c I’ve turned it down to 19c and we’ve go[en used to it now but you totally avoid the peaks and troughs it just sits at that temp all day long. We’ve now got 4kw solar too and it’s more than enough for heating plus our base energy plus an appliance say dishwasher or washer plus our dryer at the same time as its also a heatpump one and sips power. This is our usage w/c 1st April
Rich I meant to say earlier but from online info to convert oil to kwh you just multiply by 10, in your case that will be 10,000kwh.
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.I really like this guy’s thought process and using his guidance I will come up with an ASHP size. Having quickly looked through the video it looks like a 9kwh pump will do the trick.
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.Having quickly looked through the video it looks like a 9kwh pump will do the trick.
As I said the other day 9-11kWh based on floor area alone and a little knowledge ?
That said they are only guestimates as too small it will work its bollocks off and too big will cycle and inefficient!
However I would not install a heapump without carring out proper heatloss calculation as there are too mny variable.
I remembered your estimate Kezo and based on the calcs this guy comes up with I think you were bang on. I agree the heat loss is very important, especially with a stand-alone ASHP but less so in my case. If an 8kwh pump can cover me for 90% of my heating and the combi for the other 10% I’ll be happy with that.
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.I remembered your estimate Kezo and based on the calcs this guy comes up with I think you were bang on. I agree the heat loss is very important, especially with a stand-alone ASHP but less so in my case. If an 8kwh pump can cover me for 90% of my heating and the combi for the other 10% I’ll be happy with that.
I would also have a weather compensator fitted to the boiler and heatpump.
Well, carried out a heat loss survey of my house using an app supplied by “heatpunk”. Took me longer to measure the rooms, radiators, and windows than to draw the plans and work through the app. The down side is the app recommends a 16kwh ASHP and that I replace ALL my radiators gulp.
Once again, this is for a full ASHP not a high bryd system but it suggests I will be using my combi boiler a lot.
Now I have used a few different bits of kit, youtube video advice and based on these I have estimated the size of pump to be between 9 and 16 kwh obviously something isn’t correct.
My concerns about going too big is the efficiency of the unit. If it’s too big it tends to switch off and on regularly and this reduces the efficiency quite a bit. This decreases efficiency and increases cost, so not ideal.
Going by one of the “rule of thump” videos on you tube the total energy use can be used as a guide to the pump size. I used 16,500kwh of gas last year and the rule of thumb method suggests a 6kwh heat pump with a COP of at least 3 would generate 18,000kwh over the year, more than my 16500kwh used last year.
So somethings not right somewhere.
Im in the process of agreeing a deal with an installer to supply my pump, battery and solar. He is suggesting a 13kwh pump. I initially went back to him and suggested a 10kwh instead. I am now, more than likely, going for the 13kwh. Everything is telling me the 10kwh would be enough but!!!!!!!!!!
The only person who got all his work done by Friday was Robinson Crusoe.
Anything i post over three lines long please assume it is an article lol.Lets try and add some logic!
A Hybrid system’s goal, is to provide around 80% of your heating all year round or continue to do so through a mild winter. ASHP’s can potentially work in temperatures as low as -25c however, a ASHP has to work harder to heat your home below a certain threshold, typically below 0c reducing their efficiency, which is where a Hybrid system comes into play.
Most ASHP output an average of 45c, older homes especially lack the building envelope insulation of new homes being built today, will struggle more to keep the warmth in homes. This is further impacted by your location (the further north you get), along with the fact older homes have smaller radiators for traditional gas or oil fired boilers, which aren’t adequately sized for ASHP’s.
The advantage of a Hybrid setup especially in your case, as you can answer yes to the above paragraph, is you will beable to fall back on your boiler, when conditions don’t allow a heat pump to provide the warmth you require, especially as heat pumps struggle and become less efficient below 0c. There is another overlooked advantage of a Hybrid system, which is as we get older we start to feel the cold more, therefore having a Hybrid system allows you to take advantage of such a setup.
Sizing wise there isn’t much difference between a full ASHP system or a Hybrid one, because all a Hybrid system does is take advantage when the weather drops below a certain threshold, where a full ASHP would start to struggle and become less efficient. AsI have said before there are plenty of ways to get a guestimate on size require but, only one proper way and if you still have the measurements from doing the Heatpunk calculation why not do the MCS official one and see if they differ and if so by how much!
Once you are happy the sizing is correct, you can use that to gain quotes, but don’t tell the installer! Let them come to their own conclusion and if its near what you have in your head, you know the installer is on the ball park of what should be installed. Telling them what they should know/do may prove detrimental as you could loose MCS protection if something wasn’t right and the installer wrote on his sheet “customer specified” or words to that effect. By doing this if they fit a system to small to cope or to big it cycled it is the installers responsibility to put right through the MCS scheme! This does not stop you suggesting you want xyz make heat pump, solar, battery etc.
One last word weather compensation, whether implimitated or as a kit are important in the overall efficiency and running costs. If you are asked if you want it fitted or turned off or on, if standard, you should be saying yes you want it and yes turn it on in the first instance.
Enough waffle for this post, but you are 100% doing the right thing having a Hybrit system 🙂
Interesting to see these new high temperature heat pumps designed to work better in older homes.
Having said that our Vaillant Arotherm has been brilliant it’s on its own no hybrid and the house is 1930s semi right at North facing coast so we do tend to get blasted at times. House sits at whatever we set it to thru winter we were doing around £5-12 a day for all electricity for everything heating, water plus day to day. That £12 was just the occasional day where we probably turned the heat up more lol.
My only concession is I have a free electric throw from Octopus and sometimes I get super toasty under that but that’s more on me having a wonky thermostat than the house.
Yup definitely want weather compensation too. .
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