Browse Forums Heating, Cooling & Insulation 1 Jun 22, 2009 6:54 pm Got a number of quotes so far and the variation is like night and day so I am totally stumped as to which way to head. Ground floor is approx 8sq, while upper floor is approx 7.5sq. Those figures are using external dimensions of the home (not including garage). Now obviously its not really 15.5sq if using the internal dimensions of the home. Using internal dimensions and leaving out a storage room downstairs and 2 robes upstairs which will be closed doors, its really about 12sq of living area. Both the toilet and laundry will not have vents, everywhere else will. I'm not really interested in zoning. First quote - Braemar 28kw 4 star heater and Lennox 18kw refrigerated cooling. No zoning Second quote - Brivis 20kw 4 star heater and Brivis 12kw refrigerated cooling. No zoning Third quote - Brivis 20kw 4 star heater and Brivis 12kw refrigerated cooling. Upstairs/downstairs split zone for cooling. I have read that 1kw per sq is about right for cooling but have no idea for heating. But I have 3 totally different approaches to the solution. Which is more correctly specified? Is there such thing as being over spec'd in the case of cooling and/or heating? Re: Required heating/cooling capacities, what is right??? 2Jun 26, 2009 2:55 pm You can get too large a unit. This then results in short cycling where the room gets to temperature so quick the unit is constantly switching on and off, which costs you a heap in running costs. You see it often when people get wall splits for rooms, and get is too big in the hope that it will cool/heat their entire home. All that happens is it keeps switching on and off, and blowing a gale in the room it is located in. We have always worked on .15Kw per square metre for cooling and heating. We up this to .16 for raked or ceilings over 32 course. Some companies work on ratels as low as .10Kw per square metre. I think this is too low though. I am not sure how square metres compares to sq though? Re: Required heating/cooling capacities, what is right??? 3Jun 26, 2009 9:19 pm dave- I have read that 1kw per sq is about right for cooling but have no idea for heating. But I have 3 totally different approaches to the solution. Which is more correctly specified? Is there such thing as being over spec'd in the case of cooling and/or heating? These are all average rules of thumb and varies according to your climate e.g. Darwin versus Hobart. To get a proper calculation you need a heat load calculation e.g. how much sun, shading, curtains, blinds and insulation each room gets. A proper firm does a case by case assessment based on your circumstance. PS 1 square = 10 x 10 feet = 10.76 m2 10 m2 = 0.93 squares Re: Required heating/cooling capacities, what is right??? 4Jun 29, 2009 7:55 pm TheBoatMan We have always worked on .15Kw per square metre for cooling and heating. Pretty much the same then. dymonite69 To get a proper calculation you need a heat load calculation. One of the companies recommending the Brivis gear showed me calculations that he claimed were from software used by Brivis dealers. If that is the case I'd expect all the Brivis quotes to be the same equipment unless they're not genuine dealers. It suggested cooling about 7.5kw ground floor and 5kw upper floor so total of 12.5kw. Then they select a unit slightly larger. The recommendation from this 4th or 5th quote was 20kw heat/15kw cooling zoned up/down. Probably going to go with this one, hopefully its the right choice. Re: Required heating/cooling capacities, what is right??? 5Jun 30, 2009 12:00 am Do you guys have any thoughts regarding my question in this thread? A little concerned that 20kw might not be enough for 220 m2... The sales rep picked it out but I do not think he really knows - need to find out what the standard heating unit is in the house... viewtopic.php?f=20&t=19997 Re: Required heating/cooling capacities, what is right??? 6Jun 30, 2009 1:39 pm Zerosignal Do you guys have any thoughts regarding my question in this thread? A little concerned that 20kw might not be enough for 220 m2... The sales rep picked it out but I do not think he really knows - need to find out what the standard heating unit is in the house... viewtopic.php?f=20&t=19997 We have 17kW for 216m2 (175m2 conditioned area) Re: Required heating/cooling capacities, what is right??? 7Jun 30, 2009 1:44 pm TheBoatMan .15Kw per square metre for cooling and heating. We up this to .16 for raked or ceilings over 32 course. Some companies work on ratels as low as .10Kw per square metre. I think this is too low though. http://www.energyrating.gov.au/acl.html Re: Required heating/cooling capacities, what is right??? 8Jun 30, 2009 2:19 pm dymonite69 Zerosignal Do you guys have any thoughts regarding my question in this thread? A little concerned that 20kw might not be enough for 220 m2... The sales rep picked it out but I do not think he really knows - need to find out what the standard heating unit is in the house... viewtopic.php?f=20&t=19997 We have 17kW for 216m2 (175m2 conditioned area) Is that for Cooling or heating? Or both? Re: Required heating/cooling capacities, what is right??? 9Jun 30, 2009 3:54 pm Zerosignal dymonite69 Zerosignal Do you guys have any thoughts regarding my question in this thread? A little concerned that 20kw might not be enough for 220 m2... The sales rep picked it out but I do not think he really knows - need to find out what the standard heating unit is in the house... viewtopic.php?f=20&t=19997 We have 17kW for 216m2 (175m2 conditioned area) Is that for Cooling or heating? Or both? RCAC heating and cooling capacities are within 1kW of each other. The unit would have been sized for our heating needs. Re: Required heating/cooling capacities, what is right??? 10Jun 30, 2009 4:23 pm dymonite69 Zerosignal dymonite69 We have 17kW for 216m2 (175m2 conditioned area) Is that for Cooling or heating? Or both? RCAC heating and cooling capacities are within 1kW of each other. The unit would have been sized for our heating needs. Ok i'm gathering the 'conditioned area' is the inside area of the house? Not sure where I would find someone to determine what we should have considering the builder is supplying the unit... I'm putting a new floor in my kitchen, slate flagging on a standard concrete slab. 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