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    • CommentAuthordereke
    • CommentTimeFeb 7th 2018 edited
     
    I've currently got an oil boiler connected to a thermal store.
    I've had a quote to replace it with an ASHP. The quote has come in at around £10k (15kW Mitsubishi).

    At the risk of over simplifying what the installer actually does it seems to me to be a fairly simple install.

    1) detach pipes from oil boiler to thermal store
    2) install heat pump
    3) attach pipes from heat pump to thermal store

    I am sure it is a bit more complex than that of course but I thought my install would be quite straightforward so I'm a bit surprised by the price.

    Thoughts?
  1.  
    Do you have other heat sources connected to the thermal store, otherwise why use a thermal store?
    Do you have PV?
    What is driving the change ?
    Is the quote split out between parts and labour?
    • CommentAuthordereke
    • CommentTimeFeb 7th 2018
     
    Yeah we have a wood burner (though we don't use it much).
    The thermal store was installed by the previous owner.
    We also have Solar PV.

    So I am not actually convinced getting ASHP is a good idea, I was looking into GSHP as the RHI is quite good but they wanted £20k for that which is just too much.

    I'm quite disappointed in the efficiency of the boiler (a modern efficient one!) so was looking at alternatives. As I say I am not convinced of ASHP but if we it could be installed much cheaper maybe it would be workable.
    •  
      CommentAuthordjh
    • CommentTimeFeb 7th 2018
     
    Posted By: Peter_in_HungaryDo you have other heat sources connected to the thermal store, otherwise why use a thermal store?

    Because you want mains pressure hot water without pressurised cylinder inspections?
    • CommentAuthorgravelld
    • CommentTimeFeb 7th 2018
     
    Presume you have the appropriate heat emitters for a heat pump, i.e. a lot of surface area?
  2.  
    Posted By: derekeI'm quite disappointed in the efficiency of the boiler (a modern efficient one!) so was looking at alternatives.

    Can you explain a bit more about the disappointing efficiency of the (modern efficient) boiler please
    • CommentAuthordereke
    • CommentTimeFeb 7th 2018
     
    Well we just go through oil like water!

    We try and keep the house a pretty constant temperature but I've noticed the radiators are either very hot or cold. I thought with the store it would cycle the water at a more consistent temperature (from what I understand an oil boiler is either on or off it can't throttle itself down?).

    Our controls aren't great either - an analogue thermostat and on/off schedule for the boiler. Though interestingly that control has an option for heating and hot water. I'd have thought there was one supply from the boiler to the thermal store so I'm not sure how you can control either one of them?

    The previous owner was very happy with the boiler, apparently it can run on cooking oil but we don't seem to have too much of that spare anyway :wink:

    I should probably get someone who knows what they are doing to come and check it out. Maybe with some better controls we could have it working better for us.
  3.  
    We paid about that much in 2012 for a similar size ASHP. It took 2 guys best part of a week to install.
    Time mostly spent on:
    Running refrigerant pipes Between indoor/outdoor units, hole through granite wall, ceiling down for this
    Running big power cable through from fusebox, different ceiling down for that
    Powerflush existing rads
    Run new pipework as ASHP is not in same location as oil boiler
    Time allowed for removing oil boiler + flue and fixing hole in roof

    Followed by

    1) detach pipes from oil boiler to thermal store
    2) install heat pump
    3) attach pipes from heat pump to thermal store

    Then commissioning, testing, debugging.

    We got a MCS cert which prob adds a grand but was required for RHPP scheme back then.

    Looking online at the purchase cost of a big ASHP and the labour involved, I don't think the price was OTT and we saved a lot on oil bills.

    To design an ASHP system you will need to know how much heat you are using and where. Start by looking at that and you might find the oil boiler is doing OK and you can save more by adding insulation.

    Mostly ASHP is not good option for hot water or radiators but look at Daikin altherma HT which is designed to replace gas/oil boilers, two stage cycle gets a higher temperature.
    • CommentAuthorgravelld
    • CommentTimeFeb 8th 2018
     
    Posted By: derekeWell we just go through oil like water!
    That's not necessarily efficiency; that could just be demand.

    If you worked out your heat loss you'd get some idea of how well you are doing.
    •  
      CommentAuthordjh
    • CommentTimeFeb 8th 2018
     
    Has anybody looked into using car A/C equipment, or the newer 'heat pump heaters' found in EVs for space heating in a house?
    • CommentAuthordereke
    • CommentTimeFeb 10th 2018
     
    @WillInAberdeen do they all have an inside and an outside unit?
    I had thought it was a self contained outdoor unit that just had to be plumbed in. If it is more than that then the install cost is starting to look a bit more reasonable.

    @Peter_in_Hungary I guess when I said it wasn't efficient I was really meaning that running this system seems to be expensive despite it being a fairly modern efficient boiler.

    @gravelld agreed we are demanding a lot!

    As we keep our house a pretty constant temperature it seems strange to me that the radiators are either full on or full off. It seems to me it would be better to have them running constantly at a very low heat. I am not sure if that is something an oil boiler can do? Would better controls help out do you think? Weather Compensation maybe?
    • CommentAuthorGarethC
    • CommentTimeFeb 12th 2018
     
    Someone else can advise better, but I thought that you can control the flow temperature for the whole central heating circuit at the oil boiler, but that's the only control you usually have. I. E. All individual radiators can only be on at this temperature or off. The only thing e. g. thermostatic radiator valves control is how long each one comes on for (switching them off when the room target temp is reached). That is, while they might take a while to come up to their steady state temperature, they're essentially "digital" devices.
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