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Air Source heat pumps info thread!

  • 13-09-2010 1:40pm
    #1
    wclarke20
    Registered Users, Registered Users 2 Posts: 204 ✭✭


    Hi all,
    I’m in the process of deciding on my heating system. I’m looking at air source heat pumps and trying to get some info on them. I found that some info is a few years old on various forums or else buried in long threads so I thought about putting all my questions in one thread. People can add any further questions too.

    As a newbie to heat pumps I have some basic questions that I and other people may like to know. Once these are covered, we can move onto more technical questions.

    If you have any answers or opinions on these, please post. Alternatively, if there are questions I missed, post them too!


    · Can it be used effectively as the primary heat source?

    · Average water temp.?
    § Can it heat water hot enough for showers etc?

    · Can they be used in conjunction with solar, UFH etc?
    § E.g. solar heats the water first and the heat pump kicks in if the quantity & temp can’t be achieved.
    § Is anything different needed for this? Does this require separate controls, Different type of tank etc.

    · What type of system does it work best with? UFH/Rads?,
    § How many rooms would you advise doing on ground floor?
    § Would the kitchen & sitting room suffice with maybe oil back up for the rest of the house for when it gets really cold in the winter?


    · Typical running costs for a 2800sqft house. Compressor spec?
    § Would it be possible / beneficial to run it off the night rate electricity?

    · Does the efficiency drop in cold weather?

    · Can it be used with a MHRV?

    · Service schedule?

    · Installation Costs / Pump Costs ( approx figures )


Comments

  • #2
    record
    Registered Users, Registered Users 2 Posts: 34 ✭record


    Just basing my answers below on my own experience as a user of an air-to-water heating system - not an expert by any means....
    wclarke20 wrote: »

    · Can it be used effectively as the primary heat source?

    Yes, but may need to be backed up by a secondary heat source (e.g. oil boiler, stove, fire, etc.).
    wclarke20 wrote: »

    · Average water temp.?
    § Can it heat water hot enough for showers etc?

    You can set what hot water temperature you desire. The air to water unit can easily heat water to about 47 degrees. However, it is recommended that you store water at at least 60 degrees (due to legionella), so you discuss the best way to do this with your installer.
    wclarke20 wrote: »

    · Can they be used in conjunction with solar, UFH etc?
    § E.g. solar heats the water first and the heat pump kicks in if the quantity & temp can’t be achieved.
    § Is anything different needed for this? Does this require separate controls, Different type of tank etc.

    Yes, it can be used in conjunction with other systems, including solar. If the desired water temperature has been achieved through solar alone, the air to water unit will not need to activate.

    Solar panels come with their own control system, as well as very large hot water cylinders.
    wclarke20 wrote: »

    · What type of system does it work best with? UFH/Rads?,

    Air to water (or ground to water for that matter) work most efficiently when they do not have to heat the water to a high temperature. As such, they work best with an underfloor heating system, as the temperature needed for this system is relatively low. It is not suitable for radiators as these operate at about 65 degrees.
    wclarke20 wrote: »

    § How many rooms would you advise doing on ground floor?
    § Would the kitchen & sitting room suffice with maybe oil back up for the rest of the house for when it gets really cold in the winter?

    The system needs to be configured based on the size of your house, as well as the house's heat performance (e.g. how well it is insulated, etc.). This should be calculated by a qualified technician (e.g. BER assessor).

    If properly sized and if the house is suitable, it should be able to easily heat your house on all but the very coldest of days, in which case it should utilise a backup system as a boost. (Note: a backup oil boiler, for instance, can be linked in with the air to water unit and set to come on only if certain parameters are met - e.g. certain external temperature, plus air to water unit struggling to achieve sufficient output).
    wclarke20 wrote: »

    · Does the efficiency drop in cold weather?

    Yes it does. Overall though, it should be cheaper to operate than an oil / gas boiler.
    wclarke20 wrote: »

    · Typical running costs for a 2800sqft house. Compressor spec?

    § Would it be possible / beneficial to run it off the night rate electricity?

    · Installation Costs / Pump Costs ( approx figures )

    It should definitely be set to operate from night rate electricity.

    In relation to installation and running costs, the following thread may be of interest to you:

    http://www.boards.ie/vbulletin/showthread.php?t=2055263818

    The key thing with an air to water, or geothermal, system in my experience is to ensure that:
    a) your house is suitable for an air-to-water system
    b) it is installed by a competent firm - I'd definitely check a number of previous customers in that regard.


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