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Dimplex A2W Heat Pump: What's the "Use alternative power source" option in the controller UI?

  • 21-04-2022 5:31pm
    Registered Users Posts: 16 cdn16

    I recently moved to a newly built home that has a Dimplex A-class Air-to-water Heat Pump (A6MX).

    One of the options under Information is Use alternate heatsource. (Login 998) > General DHW & Heating Control > Use alternate heatsource

    I observed that the Use alternate heatsource was set (1) and the heating on both Zone 1 and 2 was working just fine. With this option, though, the compressor fan placed outside the house was not running (I've never seen it in operation). I changed the option and now Use alternate heatsource is unset (0) and the house temperature has gradually gone down and the compressor fan is in operation.

    Does this mean the heat pump isn't working as expected? While using the alternate heatsource, which I assume is electricity, the heating worked fine. I called in the electrician who worked on the property and he said there was no problem with the system.

    This is concerning as I'm paying hefty amount for electricity - Jan-Feb, it was €998 and Mar-Apr, it's €770! And I'm suspecting this could be a result of this misconfiguration.

    Any suggestions would be really helpful.



  • Registered Users Posts: 502 ✭✭✭ mike_2009

    Did you get any handover / training on the heat pump?

    Alternate source sounds like immersion or direct 1:1 heating which negates any savings the compressor unit outside would give you and hit your bills hard.

    So, I would expect your outside fan to be running - I'd take some electricity meter readings over the next few weeks and wait for the next bill and see what happens. Sometimes these systems are not commissioned correctly and items like weather compensation settings are absent to prevent call backs.

    Check out a youtube series from Heat Geeks who go into depth on heat pumps and some issues you can see. Learn more about your own - any manuals / exact model numbers will help. I'm sure it's "working" but 1/2 the problem is correct commissioning. Try calling Dimplex. Check with neighbours if you are in a development and they all have one. You need someone very experienced with heat pumps specifically, rather than an electrician. A plumber is a more likely match but you need one who focuses on heat pumps, not just old boilers etc. I can only find a generic A class heat pump manual for dimplex but you should have been left a hard copy somewhere? Is Zone 1 upstairs, Zone 2 downstairs? Do you have radiators or underfloor heating. What are the flow and hot water temps?

  • Registered Users Posts: 16 cdn16

    There was no handover. The estate agent just mentioned that we need not to change anything except for the temperature.

    We have two zones - Zone-1 being downstairs (living/dining/kitchen) and Zone-2 upstairs (bedrooms). We have conventional radiators and no underfloor heating. Usually, the daytime room temperatures would be set to 21C while nighttime it'll be around 18C and the DHW is set to 60C.

  • Registered Users Posts: 502 ✭✭✭ mike_2009

    I'd hope the setting you caught makes the heat pump do it's thing plus we're coming into warmer weather, so hopefully the bills will drop. Does your unit tell you the flow / return temp for the radiators? A low flow temp is key but only works if the Rads are sized correctly. You can reduce the hot water temp and check if it does a weekly boost for legionella but you'll have less hot water in total and it takes a good while to recharge.

    Any PV or Solar Thermal supplied with the property to offset costs?