Browse Forums Heating, Cooling & Insulation 1 Aug 19, 2015 7:41 pm Hi All First post - be gentle! I have done a search but not found a recent discussion on this, sorry if I've missed it Just signed a contract to build a two story house in Adelaide. Have always had refrigerated reverse cycle (RC) but considering our options for this build. Budgeted $12k for the RC, and the Evap + Gas heat would be about $9k - not much in it overall and I understand running costs are less with option two. RC will be the coldest but also the most expensive to run. Adelaide is quite a dry summer and humidity shouldn't be an issue for Evap A/C is required. Any comments on which way to go? Thanks in advance Mike Re: Reverse cycle Vs Evap + Gas heating 2Aug 19, 2015 9:39 pm The reverse cycle should actually be cheaper than the gas to run for heating. But then you don't need much heating in Adelaide anyhow, so the heating costs shouldn't be much an issue. One thing to watch with evaporative in 2-storey is that you'll need to run bigger ducts down, then if the gas ducts are separate, that's even more again. It really comes down to a tradeoff between the cost of running and the feel of the house. Evaporative tends to be breezier, and you look for the cool spots in the room, whereas the refrigerated tends to be more even and transparent. Evaporative encourages a more open house, where it doesn't matter so much if people open doors to go in and out. An evap unit is also good for changing over the air in the house once the air outside cools down. So they can work well at cooling a house down after you come home, but if it's still very hot outside they may struggle to cool it down as quickly as a refrigerated unit. While evap is cheaper to run, some people will also tend to run them longer to pre-cool the house so they can cope with the hottest part of the day. For an equivalent comfort you also need the air to be cooler to offset the humidity. If you're using it in conjunction with ceiling fans, then the air movement from the fans will achieve more in the lower humidity. We're looking at a similar question with our place, and I'm leaning to RC ducted again. in our current house we're spending around $500 a year on heating and cooling, and a significant part of that could be supplied from solar power. After factoring in water use and regular maintenance of the evap unit, the cost differences don't seem such a big issue in the context of all the costs to have a house. Re: Reverse cycle Vs Evap + Gas heating 3Aug 19, 2015 11:24 pm Thanks oneJohn. Helpful, although I'm no nearer deciding! The appeal of the reduced running costs is high, and I like the gas ducted heating that I would run alongside more than the reverse cycle heat we currently have. I understood gas heating to be cheaper to run than reverse cycle, are you saying this is not the case? We are also planning a fireplace (gas) so the ducted gas will only be upstairs and the fireplace will heated the family room and include a duct to the theatre room. Choices choices..... Re: Reverse cycle Vs Evap + Gas heating 5Aug 20, 2015 10:04 am Adelaide has fairly high gas prices, and they seem to be rising faster than electricity. Last time I calculated, reverse cycle ducted A/C was a bit cheaper than gas for heating. Working of figures of Electricity: 34c/kWh (peak) Gas 4.43c/MJ (16c/kWh) But the A/C has a COP in the range of 3 to 4, meaning say 350% efficiency in turning electrical energy into heat energy inside the house. while the Gas is only about 80% efficient or so in converting gas energy into heat. So you get something like 10c/kWh of actual heat for electricity, and more like 20c/kWh for gas - making gas about twice the price to run compared to electricity for heating. Re: Reverse cycle Vs Evap + Gas heating 6Aug 22, 2015 8:52 am One John is certainly right in that these days with rising gas prices and more efficient technology that RC heating can be on par or cheaper than gas ducted. It depends on the model your looking at and of course your gas rates. You can get the data you need usually from the spec sheets. Last I looked for myself, the entry level smaller models would have cost the same but the bigger units become more cost effective. For what it's worth I'd get the evap cooling and spend the savings on double glazing, better insulation, different cladding or ceiling fans. -Phil Re: Reverse cycle Vs Evap + Gas heating 7Aug 22, 2015 9:51 am Thanks guys - so far I've just gone on the words of the salesman (risky!) and my mind struggles to compute kWh stats to compare the various options! I accept and appreciate your comments oneJohn and Philip_J and will keep searching. It's a sizable house with a 'fair' budget for the RC system, although the builder hasn't yet provided the spec. I hope it should be a reasonably efficient unit. We've already included extra upgraded insulation and have got uPVC double glazing in too. Phil - you say you'd go with Evap cooling, how would you heat? Re: Reverse cycle Vs Evap + Gas heating 8Aug 22, 2015 11:20 am Ohh, naturally I meant I'll be using evap cooling coupled with gas ducted heating. I too will be having a fire, albeit a free standing wood heater version. Good job on getting uPvc DG windows! Ultimately if you've got the budget and dont mind paying a bit extra running costs for the RC cooling you will be more comfortable in the long run, especially with the glazing. I work for your power distributor so I know what sort of heat waves you get over there 4 7893 I want to build a decking to the drawn shape outlined in black. The problem is how close can I build to the gas hot water unit? Will I be able to build around it and be… 0 16155 you need a fridgie to answer but I would think you vac the whole system then add gas if you have a leak, unless it is new install with the gas already loaded, in that case… 1 2323 |