Browse Forums Heating, Cooling & Insulation 1 Apr 16, 2016 10:46 am Hi, I've just purchased a house that has a Daikin RZP145DV1 ducted reverse Cycle AC unit and I was wondering how much solar I would need to run it and the rest of the house. Thai Daikin ID panel says it has 14.5 kW Cooling Capacity and 16.0 kW Heating capacity. I guess battery back up would be good for night use but is it worthwhile waiting for battery technology to evolve a bit more? We are in Canberra and suspect it may be mostly used for heating. We had planned to use hydronic heating but as this unit already exists and appears to not be that old it seems wasteful to get rid of it. Re: Reverse Cycle AC and solar 2Apr 20, 2016 10:34 pm Heya Juxtaposer, Okay the Daikin Unit you have has the following specs... So the specs you mentioned before are the cooling/ heating capacities. Easy way to explain it... Air Conditioning has a Co-efficiency of Performance (COP) of around 3 (and a bit) Meaning for every kilowatt of power that goes in (used) three kilowatt come out (technically is moved) So your machine has... Cooling Rated Capacity (kW) 14.50 Capacity Range (kW) 6.4 - 15.5 Heating Rated Capacity (kW) 16.0 Capacity Range (kW) 6.8 - 17.2 Rated Power Input Cool (kW) 5.30 Heat (kW) 4.90 So its very hard to judge to say how long your unit runs for as it will change every day with ambient temperatures changing, different heat loads etc. But if your Air Conditioner was running at 100% cooling or heating capacity even the biggest solar system would be maxed out - in saying that no inverter machines run at 100% for long. Hope that helps, happy to do some calcs for you if it helps Re: Reverse Cycle AC and solar 3Apr 29, 2016 8:13 am Juxtaposer I'm in the exact same position as you, except my situation doesn't exist yet... We are building (also in Canberra) . Further to notsomot's post, the numbers you need to concentrate on are the inputs not the outputs of the unit. And being in Canberra the figure you are looking at the most is 4.9kW for heating. The most the unit will draw is 4.9 to pump out 17.2 (very efficient heating hence why we are going for it), but it will never be running at max. What we will be doing is monitoring power use for a full year before installing the appropriate solar system. Not be frugal with use, just normal use. Another benefit to waiting is that the Telsla Battery will hit the market soon and then that's when things will get really competitive. The thing with Canberra is that our electricity is very cheap compared to other states. Advice I've received from those in the know and have broken it down for me to see for myself is that the cost of using your own power in a battery living in Canberra isn't worth it. You get more benefit from putting that money into a bigger system, and getting credit back during the day. Ie the difference between the credit and the rate charged is low enough to justify it. Looking at melbournes rates for instance and you can see that living down there a battery is definitely the way to go. It's nice to think that you can use your own power in the evening, a terrific idea considering its peak use time and "free"... But you still have to look at the numbers. Wait a year (or at least over the winter period coming up) and purchase a good power monitor that logs usage for you. You can do it manually by checking meter every single day, but that'll get tiring very quickly. If you have cash to spend invest in double glazing. Should be mandatory in Canberra!!! That'll save you a stack of money in heating and cooling, which then means smaller solar power system. Re: Reverse Cycle AC and solar 4Apr 29, 2016 8:46 am Canberra has very cold nights and the COP of a heat pump reduces as the temperature drops. I lived in Canberra and my heat pump just iced up on cold Canberra nights. When this happened a significant amount of energy went into de-icing the outdoor coils not heating the house. Re: Reverse Cycle AC and solar 5Mar 05, 2017 4:19 pm Hi all I'm also toying with this idea, although my current position is that it probably doesn't quite work out. Given now the export rate for solar is a paltry 7c/kWh you would want to use as much as possible in the house. My first thought was great, if the RVAC needs 5.4kW to run, then a 5.5kW solar system with some smart on/off technology should be fine, either in winter or summer. However the reality seems to be you'll seldom squeeze that level out of your panels, and only for a few hours during the middle of the day in summer. In winter the panels generate about 1/2 capacity at best from what I could see. I used pvwatts.nrel.gov to get a local summary of daily solar availability and it would work, sort of, but you would still be dipping into the grid for a bit when clouds came over/cloudy days/etc. Re: Reverse Cycle AC and solar 6Mar 08, 2020 6:03 am How did you go with this? Is it on single phase? Brett philbert83 Hi all I'm also toying with this idea, although my current position is that it probably doesn't quite work out. Given now the export rate for solar is a paltry 7c/kWh you would want to use as much as possible in the house. My first thought was great, if the RVAC needs 5.4kW to run, then a 5.5kW solar system with some smart on/off technology should be fine, either in winter or summer. However the reality seems to be you'll seldom squeeze that level out of your panels, and only for a few hours during the middle of the day in summer. In winter the panels generate about 1/2 capacity at best from what I could see. I used pvwatts.nrel.gov to get a local summary of daily solar availability and it would work, sort of, but you would still be dipping into the grid for a bit when clouds came over/cloudy days/etc. Re: Reverse Cycle AC and solar 7Mar 08, 2020 7:11 am All fine in the end. The solar is single phase but at least in ACT they average out the import On 3 phases v domestic use/export of solar on 1. So over winter middays and summer afternoons we run the RVAC on a timer using the solar. The things that actually made a big difference to heating were the north-facing aspect and insulation (which I wish I got more of!). The summer western sun beats in so once the shade trees establish I hope that will make a difference. halcyon545 How did you go with this? Is it on single phase? Brett philbert83 Hi all I'm also toying with this idea, although my current position is that it probably doesn't quite work out. Given now the export rate for solar is a paltry 7c/kWh you would want to use as much as possible in the house. My first thought was great, if the RVAC needs 5.4kW to run, then a 5.5kW solar system with some smart on/off technology should be fine, either in winter or summer. However the reality seems to be you'll seldom squeeze that level out of your panels, and only for a few hours during the middle of the day in summer. In winter the panels generate about 1/2 capacity at best from what I could see. 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