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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
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    • CommentAuthorjms452
    • CommentTime4 days ago
     
    We live in a small fairly well insulated house, three up - three down and also have 4kWp PV which also does hot water in summer, MVHR and modern Veisman 7-13kW system gas boiler.

    If we heat a single room downstairs (e.g. run a wood burner or just cook - with the kitchen at the bottom of the stairs) then we don't need the heating on unless it's super cold.

    This made be wonder about the viability of a supplementary single room air to air heat pump to heavily cut our carbon emissions without huge expense - 2kW would do for all but the coldest weather with the gas to do winter hot water. Looks like I can get cop 4-5 with something like this:

    https://www.worcester-bosch.co.uk/img/rac_assets/erp/single_units/Single_Split_2.6kW_Product_Data_Sheet.pdf

    Is this a good idea and any suggestions as to unit - low power is good to maximise the PV input.
  1.  
    Seems like a good idea to me.
    • CommentAuthorjms452
    • CommentTime3 days ago
     
    Any unit recommendations and feel for cost?

    Is it a lot more expensive if we has one external fan unit going to two internal blower units - one of upstairs and one for down (all close together)?
    • CommentAuthorJeff B
    • CommentTime3 days ago
     
    jms452 - I am going through the same thought processes as you! We are in a detached dormer bungalow in which I have installed a lot of insulation, both in the attic and IWI upstairs. Although there are 4 radiators in the rooms upstairs they are permanently off as the heat rising from downstairs keeps the upstairs at around 20C. As we spend most of our time either in the kitchen/diner or the lounge I am thinking of an air-to-air ASHP just to supply the lounge and kitchen. A split unit would be good, maybe one blower unit in the lounge and one in the hallway.

    A friend of ours has had a Worcester Bosch Greensource air-to-air unit for many years. He is in the same situation as you i.e. has gas C/H and uses the Greensource when there is no requirement to have the entire C/H system working. It is situated in his hallway and by leaving the kitchen and lounge doors open, heats those rooms too. It works well and I think would definitely be the sort of thing you are looking for. I think his is 2kW but I can check if you are interested.

    We have a wood pellet boiler which does C/H and DHW (the latter only for about 7 months a year as we have solar thermal). I have been disappointed with this (for many reasons!) and if I had my time over I would not have opted for biomass. RHI payments will stop next October, hence now looking at ASHP's. There is a huge choice of air-to-air systems from what I can see already but my main dilemma is to find a long established local installer who would come and take a look at our place and offer independent advice! One question I am wrestling with is do I go for a multiple split air-to-air system or do I bite the bullet and install a full blown air-to-water ASHP system.
    • CommentAuthorjms452
    • CommentTime3 days ago edited
     
    Hi Jeff,

    Do you know if air to air needs servicing every year? - ends up being quite a big fraction of the total expense...

    Full blown air to water is definitely overkill for us - particularly as they seem pricey - so pricy we already decided to stay with a gas boiler for the main CH and hot water.

    Do you have a feel for a what's a good CoP and install cost?

    This sort of thing looks higher spec with claimed CoP of 5.3:
    https://www.aircon247.com/p/1087129/toshiba-daiseikai-25kw-super-inverter-high-wall-split-system.html
    • CommentAuthorowlman
    • CommentTime3 days ago edited
     
    Go for it; I've had my Toshiba R32 inverter ducted system for over a year now, and I would not go back to any form of wet CH.
    Heating the air direct instead of the intermediate stage of first heating water seems the way to go for me. Also, to select an A2W heat pump just to get the perceived added benefit of some DHW spin off seems equally pointless. You can directly heat the water more efficiently with electricity, especially if you have PV to supplement your grid consumption.

    If you're considering going down the heat pump route anyway it may be worth looking at a slightly larger model with split capacity and putting in two or more indoor units. The extra hardware costs may not be too great.

    As for which manufacturer to go for; there are loads. My advice would be to stick with the established makes, but your choice of F gas fitter may have some bearing, as they all have their particular likes often merely based on the amount of units they fit and, I guess, the trading discounts they receive rather than any pluses and minuses of the units themselves. The aesthetics of the indoor units is also very important, as is their noise output. They vary too with the sophistication of their air distribution. I don't know how the indoor unit/s will impinge on your MVHR but the room siting may need careful consideration.
    If you want to have some DIY input and you're reasonably handy find an independent fitter who would be prepared to let you do some of the legwork,- it's what I did. This could include preparing an outdoor hard standing, basic cable runs etc. and in my case trunking layout and condensate drains. That just left the fitter to put in the copper refrigerant pipework, with my help, and testing and commissioning. Your fitter may even let you buy all the stuff yourself, mine did.
    • CommentAuthorJeff B
    • CommentTime3 days ago
     
    Posted By: jms452Hi Jeff,

    Do you know if air to air needs servicing every year? - ends up being quite a big fraction of the total expense...

    Full blown air to water is definitely overkill for us - particularly as they seem pricey - so pricy we already decided to stay with a gas boiler for the main CH and hot water.

    Do you have a feel for a what's a good CoP and install cost?

    This sort of thing looks higher spec with claimed CoP of 5.3:
    https://www.aircon247.com/p/1087129/toshiba-daiseikai-25kw-super-inverter-high-wall-split-system.html


    I would be wary of very high COP figures. I usually look for the worst case situations e.g. outside -7C and flow temperature of about 30C. If you can a COP of 3 or more under those conditions then that would be very good.

    As Owlman has said there are other factors such as noise (external noise is no issue for me as we have a large garden) but internal might be critical. We have Mitsubishi blower units in our church and they are whisper quiet.
    The Toshiba unit that you found looks good in this aspect. I see it has a 5 year warranty but this is dependent on regular servicing which as you say could be expensive - I have not looked into this aspect. The units we have at our church are about 7 years old and apart from regular cleaning of the filters on the internal blower units they have had no maintenance/servicing per se. I would question what servicing is required in reality, other than just a check on the general condition of the outdoor unit e.g. dirt/leaves on the heat exchanger grill?

    I don't have any idea of installation costs yet. Are you a DIYer? Myself, I could do most of the installation except for the connections which require the use of an F gas fitter. I don't know what are the chances of finding a friendly fitter (as Owlman did) in our neck of the woods but I am still at the early stages of my investigations.

    At the price of these systems compared to a full-blown air-to-water system I'm thinking I could install multiple units side by side and replace my entire heating system. There must be a snag there somewhere though - maybe other more experienced folk on the forum will put me right!

    Good luck with your project. Please keep posting on your progress, I for one would be very interested.

    Jeff
    • CommentAuthorJeff B
    • CommentTime3 days ago
     
    https://www.worcester-bosch.co.uk/img/rac_assets/erp/single_units/Single_Split_2.6kW_Product_Data_Sheet.pdf

    COP at -7C/20C = 3.0
    • CommentAuthorJeff B
    • CommentTime3 days ago
     
    Owlman - thanks for your input. I know you have posted some ideas on this subject before on the GBF, having had experience with air-to-air (in half your house IIRC?). Your thought about selecting an A2W heat pump just to get the perceived added benefit of some DHW got me thinking. Couldn't I use Economy 7 electricity to heat my DHW tank during the night in the winter months and therefore eliminate the need for the wood pellet boiler to do this? If air-to-air can do the space heating, then bingo the pellet boiler is redundant.

    I am thinking about changing our electricity supplier anyway, so this would be a good time to look into the various tariffs that are available, both for Economy 7 and standard daytime rates.
    • CommentAuthorowlman
    • CommentTime2 days ago
     
    Now you've got me thinking Jeff. I have no experience of Economy 7 or what the rules are for that tariff but I will look into it.
    At the moment I'm using the A2A as principle heating for the rear of my home, with the occasional log fire, ( simply because I like it and the wood is free).
    This leaves my biomass logwood boiler to provide heat for the hallway, bathroom and any other room on an, "as and when required" basis, plus DHW via a plate heat exchanger. I can alter the latter again as and when required, onto pure Solar with a simple change lever. The Solar tank also acts as a pre-heat on the PHX supply side.
    If I decide to push ahead in future with another A2A it will most likely be one or two wall hung units in the hall and bedroom end of the house.
    •  
      CommentAuthordjh
    • CommentTime2 days ago
     
    Posted By: owlmanI have no experience of Economy 7 or what the rules are for that tariff

    The rules are very simple. You get one price during the day, and a much lower price for seven hours during the night. The daytime price is typically a bit higher than a standard tariff, and the nighttime rate is a bit more than a third of it.

    Exactly which seven hours you get is a bit of a guessing game. It's up to the supplier/DNO (don't know which) and they vary it in different areas to spread the load on the grid. It also depends on what type of meter they fit - mine doesn't move with summertime, for example, but some installation do I believe.

    We use E7 to heat our DHW when the PV doesn't provide enough. I use an hour at the start of the period and another hour towards the end. The thermostats mean nothing is used unless the PV hasn't heated the water. I also added a twenty minute burst just before our normal shower time in the evening as an insurance against cold showers :)
    • CommentAuthorowlman
    • CommentTime2 days ago
     
    Hi Dave, Thanks for the explanation and it may be something to look for use with resistive underfloor heating in for instance bathrooms and possibly a storage heater in the hallway, both of which I could easily wire onto a single timed circuit as well as the A2A of course which is already on its own breaker.
  2.  
    I'd understood that the old Economy 7 / Economy 10 were being displaced by the new Smart Meter tariffs that are coming out?

    https://selectra.co.uk/energy/guides/tariffs/economy10
    •  
      CommentAuthordjh
    • CommentTime2 days ago
     
    We don't have any separate circuits, I just use timers on things wired into the normal circuits. I think there is the possibility of using a separate switched circuit from the meter but I don't remember the details I'm afraid.
    • CommentAuthorJeff B
    • CommentTime2 days ago
     
    From what I have been reading over the last few days it seems people with night storage heaters have separate circuits but otherwise not. I would do as djh does and simply put a timer on the immersion heater supply. In fact we already have the facility to do so. We have a Timeguard switch which is programmable but we only use it manually - it has fixed 1 hour and 2 hour settings. 1 hour is normally sufficient. I got it because I wouldn't like to use "run of the mill" timers for a 2 or 3 kW heater!
    • CommentAuthorJeff B
    • CommentTime2 days ago
     
    djh - yes, I can concur that although the night time tariff is about one third the daytime cost I have yet to ascertain what the daytime cost will be. As I am thinking of changing electricity supplier, this will be one of the things I will be looking out for. I wouldn't want to be paying OTT for daytime usage whilst only making a small saving on Economy 7!
    • CommentAuthorowlman
    • CommentTime2 days ago
     
    At a very quick glance it appears that not all providers do Economy 7, so that may be the first stumbling block. I'm not on a bad tariff at the moment, so as you say it'll involve a bit of number crunching, but I'm not dismissing it just yet.
  3.  
    Posted By: owlmanHi Dave, Thanks for the explanation and it may be something to look for use with resistive underfloor heating in for instance bathrooms and possibly a storage heater in the hallway, both of which I could easily wire onto a single timed circuit as well as the A2A of course which is already on its own breaker.

    I'm not so sure that electric UFH in the bathroom is something that you would want to put on a might time only supply, you would get a nice warm bathroom about 3 am....not really when you want it. An electric storage heater, well that's a whole different matter.
    • CommentAuthorowlman
    • CommentTime1 day ago
     
    Hi Peter, Does Economy 7 tariff change at 3 am or, are all providers different?
    •  
      CommentAuthordjh
    • CommentTime1 day ago
     
    Posted By: owlmanHi Peter, Does Economy 7 tariff change at 3 am or, are all providers different?

    No, PiH was just using 3am as a time in 'the middle of the night', I think. E7 periods are almost all between midnight and 8am, but exactly when they start and stop varies a bit, and of course they're only seven hours, not eight.
  4.  
    Posted By: owlmanHi Peter, Does Economy 7 tariff change at 3 am or, are all providers different?

    I don't know - I just picked 3am as an arbitrary time by which time the bathroom would be nice and warm after several hours of cheap night time rate electricity.
    Economy 7 is used to balance the load on the grid by moving load from daytime to nighttime by price incentive so different providers could conceivably have different times depending upon their load profile.

    I don't know how smart meters could / would restrict certain loads (e.g. storage heaters) to low tariff times only.

    Over here the night rate has a separate meter which is frequency switched over the grid so that the providers an control when power is applied (with a guaranteed 8 hours minimum a day but weekends is 24 hours) only certain types of appliances are allowed e.g. fixed wired storage heaters, heat pumps (COP 3 or higher) and water heaters.
  5.  
    There's also Economy 10, which has a few cheap hours during the daytime hours and some more overnight. Don't know if you can still get E7 or E10 meters installed, but you can get a free smart meter which will work with an E7/E10 tariff.
    https://selectra.co.uk/energy/guides/tariffs/economy10#what-is-an-economy-10-meter

    Other emerging Smart Meter tariffs range from one with 21 hours of slightly-cheaper electricity throughout the daytime and nighttime with 3 expensive hours in the evening peak. At the other end there's offers with 5 very-cheap hours in the wee small hours. Some give you more cheap hours at the weekend.

    The UK smart meters do not physically switch anything on themselves (due to data privacy etc), instead you set your own timeswitches or smart plugs or hive-type thermostats to come on the cheapest time. Or just turn stuff on yourself when you want it, and be billed at the prevailing rate for the hours you have it on.
    • CommentAuthorowlman
    • CommentTime1 day ago edited
     
    When I retiled my hallway and kitchen floors, I installed resistive cables and although I haven't used them much they were relatively cheap and easy to do so I decided on a bit of future proofing. They do heat up quite quickly so in a bathroom, two or three hours would suffice to produce a meaningful result. Plus, the 1/2" stone tiles do retain heat.

    From what you say It does seem like the Hungarian providers are much better organised with their night rate, and their appliance restrictions don't sound unreasonable, although maybe difficult to police, I guess.
    • CommentAuthorEd Davies
    • CommentTime1 day ago
     
    My expectation would be that E7/E10 will disappear in the next few years to be replaced by variable tariffs which reflect demand and renewable generation so it's probably worth at least thinking about options for control more flexible than simple time switches spread round the house plus means to store heat in various forms (water tanks, slabs).
  6.  
    Posted By: owlmanFrom what you say It does seem like the Hungarian providers are much better organised with their night rate, and their appliance restrictions don't sound unreasonable, although maybe difficult to police, I guess.

    Yes it is difficult to police - they don't - and to some extent they don't care. The aim is to shift load from day to night and weekends so if someone uses, say a freezer or washing machine on the night meter then the object is achieved as it is load moved from day to off peak, and don't forget the provider switches the meters on and off to control the baancing.
    •  
      CommentAuthordjh
    • CommentTime1 day ago
     
    Posted By: Ed DaviesMy expectation would be that E7/E10 will disappear in the next few years

    I think it may take longer than that just because of inertia. Who's going to force me to get my tariff and meter changed?

    options for control more flexible than simple time switches spread round the house plus means to store heat in various forms

    The Timeguard switches have four switchable periods a day and can switch weekdays and weekends separately, so they're fairly flexible. But I've replaced the timer I used with my MVHR post heater with a remote-controlled plug that I control with cron jobs run on my emonpi system. So it's not too difficult. As you say, the ability to store the electricity as heat in a water tank or in the the structure of the building (or a storage heater!) is key to making it work/pay. Battery prices aren't yet at a level where they're a good alternative IMHO.
    •  
      CommentAuthordjh
    • CommentTime1 day ago
     
    BTW, is anybody aware of a product that can be used as the 'inside unit' of a split air-air HP which can heat air in a duct? Either a dedicated duct heater or something that could be adapted to the purpose. I'm wondering about replacing my current duct heater with an ASHP powered unit.
  7.  
    Posted By: djh Who's going to force me to get my tariff and meter changed?
    Posted By: djh elsewhere re: electricity price increases night rate +18% !!!

    It's perhaps worth changing tariff yourself before anyone forces you to - if you stay on a legacy tariff for too long then the price will only go in one direction....! Inertia can be expensive, but for the same reason, I agree that the energy co will want to keep people on the legacy tariffs for longer than might reasonably be expected.

    With the increase in car charging, electricity prices in the evening peak are likely to increase, to ration usage. So Time of Use tariffs should become more attractive, possibly replacing E7/E10.

    How about https://www.orionairsales.co.uk/ducted-air-conditioning-28-c.asp ? Presumably they don't heat the air as hot as a direct electric heater does (to keep the CoP up) so you need to move more air?
    • CommentAuthorJeff B
    • CommentTime1 day ago edited
     
    Posted By: djhBTW, is anybody aware of a product that can be used as the 'inside unit' of a split air-air HP which can heat air in a duct? Either a dedicated duct heater or something that could be adapted to the purpose. I'm wondering about replacing my current duct heater with an ASHP powered unit.


    I came across this:

    https://ampair.co.uk/products/?product_types=ducted

    Is this the kind of thing you are looking for?
    • CommentAuthorEd Davies
    • CommentTime19 hours ago
     
    Posted By: djhBut I've replaced the timer I used with my MVHR post heater with a remote-controlled plug that I control with cron jobs run on my emonpi system.
    Yep, something like that that looks at the time-of-use tariffs for the next 24 hours and decides when to heat is what I had in mind. I.e., don't build in the time clocks too much; you want to future-proof by arranging for all the high energy use things to at least have some way to be modified to be controlled remotely without too much cost or disruption.
   
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