Browse Forums Heating, Cooling & Insulation 1 Jul 14, 2010 8:10 pm We are about to start a new build and I researching options for heating and cooling. We have a largish single storey house in Melbourne, about 400sqm of living area. I have received a quote for an invertor based system and a gas/electric system; both quotes come in at about the same price ~$24k installed. Invertor: Actron SRM230E ‘ESP ULTIMA’ Gas/Electric: Lennox 1 x G61MPVT-60C-11, 1 x G61MVPT-60C-090, 1 x TSA048S4-3, 1 x TSA06054/3 I am really confused which way to go. I get the sense that each installer is promoting the supplier they are more aligned with, rather than the best solution for me. My initial intention was to go with what I'm used too (gas/electric), but now I leaning more towards the invertor. I'd be interested in peoples throughts on the following questions: - In terms of running cost, which option provides the most efficient running costs for heating? - Does one technology heat and cool more quickly than the other? - Does the heating from the invertor provide the same form of radiant heat as its gas equivalent? - In terms of running cost, which option provides the most efficient running costs for cooling? - Does one technology require more maintence than the other? - Is invertor technology the same as reverse cycle? So many questions ..... Re: CONFUSED - Invertor or Gas/Electric ???? 2Jul 15, 2010 12:24 am Both AC and gas heaters condition the building by heater air (convection) not by radiant heat. Radiant heaters are things like wood fires, hydronic heaters or bar radiators. Actron is a reverse-cycled refrigerative AC. Lennox combines a gas heater with a cooling-only refrigerative AC. A reverse-cycle AC (RCAC) is able to heat or cool using the same heat pump technology. RCAC units tend to more expensive than the cooling-only variety. Inverter technology is a advanced variant of AC produced by some manufacturers. Rather than switching on-off to maintain temperature it can vary its output depending how close it is to the target temperature. They may reduce energy use up to 10%. Inverters are more expensive than non-inverters. Actron Ultima is another incremental step in efficiency. They can lower its inverter output and air flow to only condition one room. Other inverter ACs will deliver air flow too high for a small area and will constantly switching on and off to maintain temperature. The sizing of the unit is based on the calculated heating and cooling loads of the house. A rough of thumb is 0.15kW/m2. e.g 300m2 of conditioned area will require a 45kW unit. However an energy-efficient house might need half of this. Of course you can get away with a smaller unit if you aren't anticipating that you will simultaneously condition this amount. Note that an oversized unit that is normally used to condition a small area will work far less efficiently. Zoning also makes a difference to your running costs. Heat pumps work on the same technology as fridges. The main issues are loss of refrigerant or failure of the compressor. Gas heaters are simpler in design. However, the actual cost of running the unit is mainly based on the unit cost of the energy source and the efficiency of the appliance. Generally MJ for MJ gas energy is 75% cheaper than electrical energy. However, AC (heat pumps) are 3 x more efficiency. Considering the two effects, gas ends up about 25% cheaper when used for heating. However, your mileage may vary depending on the actual energy costs in your area and efficiency of the unit. For cooling it may be possible to obtain a 10% reduction in running costs with a high-end Actron unit versus a cooling-only non-inverter rebadged brand from Lennox. Nevertheless, in most regions in Australia with a mixed climate, heating costs tend to be the dominant part of the energy bill rather than cooling. Therefore the added benefits of a more efficient cooling unit may not be that significant. Finally there are many other factors that influence your running costs more than the heating/cooling unit. If your house is well designed to get lots of sun in winter and well insulated then you can reduce your heating costs by over 50%. Similar gains could be obtained by keeping the house (particularly the windows) well shaded during summer. See: Passive cooling Passive heating Re: CONFUSED - Invertor or Gas/Electric ???? 3Jul 15, 2010 7:31 pm Thanks dymonite69 for your very comprehensive and informative post. I am big on onging energy effeciency (and cost), therefore I'll go the route of gas/electric. Dymonite69 or anyone, as you can see from my original post, I have been recommended 2 x Lennox gas furnaces, and 2 x Lennox add-on air conditioners for my home. Are the Lennox brands at the better end of the spectrum, and is there another brand that can get me a comparable output without having to have 2 of each units?? Re: CONFUSED - Invertor or Gas/Electric ???? 4Jul 15, 2010 7:58 pm The spec data: Lennox Brochure shows the heaters to be 24.6 KW and 30.5 kW = 55.1 kW total. The add on cooling gives 17.5 kW + 17.5 kW = 35 kW The Actron Brochureindicates that the SRM 230E provides half the capacity. 23.5 kW heating or 23 kW cooling Re: CONFUSED - Invertor or Gas/Electric ???? 5Jul 21, 2010 4:49 pm Just me being pedantic But the Actron Air uses a digital scroll compressor not an inverter compressor. The Scroll Compressor uses an unloader to control capacity. The Inverter compressor uses stepped speed control to control capacity. Hi everyone! 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