Johh Posted February 8, 2023 Share Posted February 8, 2023 I was hoping to get a ASHP system installed in conjunction with solar to replace our oil system. We do not have mains gas. We only have electricity supplied on a one phase system and I am being told it won’t be powerful enough for a system to heat a 300sq m house. Is this correct? What other options do I have? Thanks Link to comment Share on other sites More sharing options...
Jenki Posted February 8, 2023 Share Posted February 8, 2023 You need to look at your heat requirements now i.e. what is the requirement in KWH to keep you house warm, what is your hot water requirements etc.. how well insulated and airtight your house is. once you have figures, then you can post them on here and good advice will follow. 1 Link to comment Share on other sites More sharing options...
IanR Posted February 8, 2023 Share Posted February 8, 2023 How much oil do you use a year? and do you have any other space heating installed, ie. log burner etc. A well insulated and airtight 300m² house could be comfortably heated with an 8kW ASHP. But, how good is your insulation and are you prepared to update? Link to comment Share on other sites More sharing options...
PeterW Posted February 8, 2023 Share Posted February 8, 2023 Just now, Johh said: We only have electricity supplied on a one phase system and I am being told it won’t be powerful enough for a system to heat a 300sq m house So let’s start with the heat loss calculation and then can decide if this statement is true, along with the heat emitter you are using (UFH / Rads) and then you can decide what heat input you need. From that, you’re into the spec of the ASHP which will cap out at around 16kW output. On a COP of 2.5, that’s about 27A max current. Single phase supplies are 80A or 100A in the UK unless you’re on an old pole transformer so you have no issue with using single phase unless you’ve got a horrendously leaky and poorly insulated house… Link to comment Share on other sites More sharing options...
Johh Posted February 8, 2023 Author Share Posted February 8, 2023 Peter, Jenki and Ian many thanks for the replies. I’ve included floor plans for the upcoming work later this year. You can get a comparison of the current floor plans from my profile. At the moment nothing has been done for years and there is poor insulation and single glazed windows. We installed log burners in the two ground floor rooms on the left hand side of the plans as there is an abundance of logs here. We will insulate throughout as well as the installation of new windows. At the moment the log burners keep the two rooms very warm and are 8kw each. But the rest of the place is cold as soon as the heating goes off. We don’t know how much energy (oil) we currently use as we are between two houses at the moment. I know that we have 100a electricity supply and that we will be installing UFH throughout the ground floor. Apologies for my lack of technical knowledge. Link to comment Share on other sites More sharing options...
IanR Posted February 8, 2023 Share Posted February 8, 2023 28 minutes ago, Johh said: I’ve included floor plans for the upcoming work later this year... We will insulate throughout as well as the installation of new windows... we will be installing UFH throughout the ground floor... Since you are planning a significant refit, including ground floor UFH, you have plenty of opportunity to insulate well and improve air tightness. There should be no issue providing space heating and hot water from a single phase powered ASHP, but you'll need to calculate the predicted energy loses and pay careful attention when the work is done to ensure no corners are cut. Link to comment Share on other sites More sharing options...
JohnMo Posted February 8, 2023 Share Posted February 8, 2023 35 minutes ago, Johh said: installing UFH throughout the ground floo Hope you have the floor well insulated, otherwise heating could cost you more instead of less. Just to throw another spanner in the works. 3 Link to comment Share on other sites More sharing options...
SteamyTea Posted February 8, 2023 Share Posted February 8, 2023 2 hours ago, Jenki said: You need to look at your heat requirements now i.e. what is the requirement in KWH to keep you house warm, It is more usual to use power per degree temperature difference, this gives you a kW/K metric. kWh is the amount of energy used and is a function of the time the house is heated, what the 'h' is, hours. You can quote kWh/year, or any other secondary period i.e. day, week, month. But when it comes to sizing a system, kW//K is more useful as you can make assumptions about minimum external temperature and internal temperature. Eternal temperatures can easily be modelled from the CET temperatures. If you take a mean external temperature of 10°C, and a standard deviation of 5.2°C, you can do a normal distribution curve in a spreadsheet that closely resembles reality. Multiply results by 100 to make it a percentage of time. If you want to be on the safe side for heating, the 1980 to 1990 mean temperature is 9.5° and SD 5.3° If worried about cooling, then the mean is 10.2° and the SD is 5.2°C. 1 Link to comment Share on other sites More sharing options...
Jenki Posted February 8, 2023 Share Posted February 8, 2023 2 hours ago, SteamyTea said: It is more usual to use power per degree temperature difference, this gives you a kW/K metric. When I typed KWH I thought of you @SteamyTea. In my defence I thought this was a figure he may have easier access to. Link to comment Share on other sites More sharing options...
saveasteading Posted February 8, 2023 Share Posted February 8, 2023 59 minutes ago, Jenki said: When I typed KWH I thought ... .....hee hee, this will really wind SteamyTea up. I will type Kelvin Watt Hertz instead of kWh. Link to comment Share on other sites More sharing options...
Iceverge Posted February 8, 2023 Share Posted February 8, 2023 5 hours ago, Johh said: We don’t know how much energy (oil) we currently use as we are between two houses at the moment. I would certainly hold off on the ASHP if you don't know how much energy you are using. Could you requisition the oil bills from the previous owner? Link to comment Share on other sites More sharing options...
Marvin Posted February 9, 2023 Share Posted February 9, 2023 Nothing has been mentioned about airtightness and wood burners: Are the wood burners room sealed? Link to comment Share on other sites More sharing options...
JohnMo Posted February 9, 2023 Share Posted February 9, 2023 1 hour ago, Marvin said: Are the wood burners room sealed? They should be taking outside air in via a dedicated inlet. Also the stove needs to take all air from this duct, some don't 1 Link to comment Share on other sites More sharing options...
Marvin Posted February 9, 2023 Share Posted February 9, 2023 5 minutes ago, JohnMo said: They should be taking outside air in via a dedicated inlet. Also the stove needs to take all air from this duct, some don't Hi @Johh When you upgrade the insulation to a building including the floor, walls and roof, a far greater percentage of the heat loss is caused by poor air tightness. If we were to turn off our MVHR and use trickle vents in winter our energy requirement to replace the heat lost through the air changes (at 6C outside, 20 inside) would rise from 175Watts to 875Watts causing a 67% increase in the energy required to heat our home. (not counting the energy used to replace the warm air extracted by the fans needed to wet rooms and kitchen) IMLHO (in my less humble opinion based on my experience) once the building fabric is highly thermally resistant, airtightness becomes more and more important when calculating heat loss. If you are not fanatical about sealing the building...... Good luck M P.S. When "guiding" the builders when completing the airtightness works on our renovation this sort of phrase was often heard: "What? you want to seal between (whatever) and (whatever) ??? Bewilderment, and a polite-ish look at me like I'm either stupid or nuts. "Never done that before!" Luckily I was on site so it was done. 1 Link to comment Share on other sites More sharing options...
Post and beam Posted February 9, 2023 Share Posted February 9, 2023 1 hour ago, Marvin said: P.S. When "guiding" the builders when completing the airtightness works on our renovation this sort of phrase was often heard: "What? you want to seal between (whatever) and (whatever) ??? Bewilderment, and a polite-ish look at me like I'm either stupid or nuts. "Never done that before!" Luckily I was on site so it was done. Really curious to know just how detailed this kind of thing can get. I would like to do a good job of this when ( if) my planning gets granted and the house can start. Not having any previous experience on site i worry that i will have no idea what to look for Link to comment Share on other sites More sharing options...
Kelvin Posted February 9, 2023 Share Posted February 9, 2023 Very detailed in theory but in practice it just needs careful thinking about how air could move in and out of the building and then careful detailing. The hardest bits are awkward junctions, where different materials comes together, making sure no unplanned penetrations are made in the barrier and if they are they are highlighted and fixed, no boxing in or covering up anything until you’ve checked it and had a preliminary airtightness test done. Your drawings should have a section with a red line around it showing where the airtight barrier is and your construction drawings should have a section on each main component of the house showing the detailing of the junctions for all the components including the airtight barrier. I did a practical course at the NSBRC which was useful. 1 Link to comment Share on other sites More sharing options...
Post and beam Posted February 9, 2023 Share Posted February 9, 2023 7 minutes ago, Kelvin said: I did a practical course at the NSBRC which was useful. Oh, on airtightness specifically or understanding the construction drawings? Interested in this Link to comment Share on other sites More sharing options...
Kelvin Posted February 9, 2023 Share Posted February 9, 2023 1 minute ago, Post and beam said: Oh, on airtightness specifically or understanding the construction drawings? Interested in this Airtightness. Half day. Bit of theory bit of selling to you, some demos, then some practicals on applying the tapes and various solutions for penetrations. Link to comment Share on other sites More sharing options...
JohnMo Posted February 9, 2023 Share Posted February 9, 2023 1 hour ago, Marvin said: When "guiding" the builders when completing the airtightness works on our renovation I got the same on a new build also Link to comment Share on other sites More sharing options...
Marvin Posted February 9, 2023 Share Posted February 9, 2023 Hi @Post and beam As @Kelvin says, not difficult to understand once you get your head around it. Link to comment Share on other sites More sharing options...
Post and beam Posted February 9, 2023 Share Posted February 9, 2023 I dont suppose it is. My job involves marking the homework of people that work in data centres. Change control and standards compliance kind of thing. But where to look and what to look for with regard to this airtightness thing is a new skill. Important to get it right as well because its my house after all. Link to comment Share on other sites More sharing options...
Kelvin Posted February 9, 2023 Share Posted February 9, 2023 Read as much as you can. Look at YouTube. Go onto the barrier manufacturer websites and look at their info. Many of them do CPDs so join them. Link to comment Share on other sites More sharing options...
Post and beam Posted February 9, 2023 Share Posted February 9, 2023 Just contacted a couple of companies that look like they do this type of training. Link to comment Share on other sites More sharing options...
SteamyTea Posted February 9, 2023 Share Posted February 9, 2023 I think part of the problem about airtightness is too much trust in the techniques used. Examples being: "We parked the walls" "All internal walls are plastered" "The windows were taped" "All insulation is sheet/board" "It is timber frame" "The VCL is the airtight barrier" "The whole house is covered in Tyvek" "It is triple glazed" Non of those are inherently airtight. As others have said, it is the interfaces that are important, and they get covered up very quickly and cannot be visually checked after the event. Then there is twats with drills. 1 Link to comment Share on other sites More sharing options...
JohnMo Posted February 9, 2023 Share Posted February 9, 2023 26 minutes ago, SteamyTea said: Then there is twats with drills. and nail guns Link to comment Share on other sites More sharing options...
Recommended Posts
Create an account or sign in to comment
You need to be a member in order to leave a comment
Create an account
Sign up for a new account in our community. It's easy!
Register a new accountSign in
Already have an account? Sign in here.
Sign In Now