Browse Forums Heating, Cooling & Insulation 1 Aug 22, 2014 6:15 pm Does anyone know a reliable formula for calculating the required kW for radiator panels based on room size, external wall size, window size etc? I'm getting varying suggestions from suppliers so don't know what to trust. Some just say 1 kW per 10 sqm, some say 1.4 kW per 10 sqm, one gave a result of 5.4 kW for a 21 sqm room, and then there is a calculator that apparently takes into account windows, external walls, whether you have insulation (see http://www.choice.com.au/reviews-and-te ... lator.aspx) E.g, what kW rating would you suggest for this room? 6m x 3.6m with 2 external walls (approx 25% of the external walls are standard windows, not double glazed). Ceiling 2.4m insulated, hardwood floors on piers with air underneath. From the formulas I have at least 3 different results, 2.8kW, 3.25 kW and 5.4 kW. Re: Hydronic heating calculation 2Aug 22, 2014 11:36 pm If you're struggling to get answers here, you may also want to check at the ATA forums, http://www.ata.org.au/forums/
There's some guys over there that are good at this sort of stuff. I guess you'd also have to take your climate into account, ie the temperature differential between the outside & your required inside temperature (along with insulation levels). Also the temperature of the heated water you are using. I've heard that if you want to use cooler water temperatures, you can up the panel sizes. See what the ATA guys have to say, tonnes of useful info & helpful people over there. Re: Hydronic heating calculation 4Sep 01, 2014 12:56 pm I've got a spreadsheet that does it for multiple rooms and accounts for U/R values for walls, windows, floors, ceilings and room types. Calculates flow rates and head for circulators. Been a labour of love as info is hard to gather. Does require you modify certain parameters by hand depending on the U/R values you can get or guess as hard to come by. Happy to share if you PM me. You can at least use it to validate other info, particularly sizing by companies giving you quotes!!!! I've validated it against various online models. Re: Hydronic heating calculation 5Sep 01, 2014 2:02 pm By the way, for your described room, with a target temp difference to the coldest day of 22degrees uplift, the heating load would be between 2.3 to 2.5kw. Assumes wall insulation of R2.5 and R4 for the ceiling. Assumes all walls are external facing. If no wall insulation, then it would increase to about 3.3kW. If only 2 walls external facing and other walls are against heated rooms, it would be about 1.8 to 2kW with wall insulation. Can't see how you would get to 5.8kW unless you left off a wall to the outside!!! Changing you target temp difference to 30 degrees (i.e external lowest temp in winter -8 and inside temp 22), would give a heat load of about 2.8kW. Does anyone have a suggestion for a good hydronic in slab heating speacialist who may be able to help me with an existing system and wether or not it may need a seperator… 0 4882 Hi, My home construction is complete, and the handover is scheduled next week. However the construction has been delayed and I have raised this to the builder. The… 0 5325 Yes you are correct, unless there are outside works which form part of the contract such as landscaping or driveways, and importantly, the work delayed is on the critical… 1 3523 |