Browse Forums General Discussion 1 Jun 15, 2013 10:32 am Hi folks I am looking at getting a ducted A/C system in my house. The power draw on the unit is rated at a maximum 21 amps. The main power feed coming into my house I believe is 55 amps, with a 45 amp main fuse. I have a gas hot water system and gas stove. I have received conflicting advice from two electricians with years of experience. One says I should upgrade the power feed to the house at a cost of $2500+, the other said I should save my money and will almost certainly be ok. The latter went through the general power draw of a few common household items, and qualified his wait and see/do nothing approach by saying that if I had a pool, spa, electric hot water system, electric stove, or a combination of any of those, his advice might be different, but given the presence of gas appliances, thinks I can get by and save myself $2500+ (probably more). My question is what is the general expected amp requirements of common household items such as: Fridge 50" Plasma tv Desktop PC Iron Toaster Electric oven Electric kettle Stereo I'd like to try and work out my maximum anticipated power draw at any one time, based on the above. If any electricians have any thoughts on the advice I've received from both parties, I'd welcome it. Cheers JT Re: General amp requirements - common house appliances 2Jun 15, 2013 10:42 am Quick check find the kw and MULTIPLY (Not divide as I originally said, I was having a bad day SORRY) by 4 (its actually closer to 4.4 if you want to get the calculator out) The big users are the oven, kettle, toaster, and Iron, fridge, freezer, the rest will be fairly small. You are not going to be using everything at once though The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: General amp requirements - common house appliances 3Jun 15, 2013 12:07 pm Not using everything at once was the key message from the second sparky who said I probably wouldnt need an upgrade. He also said the main fuses take a while to heat up before they trip, and unless there's an actual fault, there is some scope to go above and beyond the 45amps at least for short durations (boiling the kettle) etc. The A/C is 14.99KW. The A/C installer told me the manufacturer claims it requires up to 21 amps. 14.99/4.4 = 3.4 amps. Doesn't sound right... 14.99KW = 14990 watts / 4.4 = 3407 amps lol. That's not right either. What am I missing based on your suggested calculations ? Re: General amp requirements - common house appliances 4Jun 15, 2013 2:02 pm Sorry for the mistake above. Coming back to your issue If I wanted to calculate the amps for my kettle which is 2.2KW its going to be around 10amps Air conditioners are a completly different thing to something like a an electric heater as they don't use the electricity to provide direct heat they use the power to run a heat pump which extracts the heat out of the outside air. Some air conditioner can get over 200% efficiency (one Kw of power in means more than 2KW worth of power out. The Harder You Try - the Luckier You Get ! Web site http://www.anewhouse.com.au Informative, Amusing, and Opinionated Blog - Over 600 posts on all aspects of building a new house. Re: General amp requirements - common house appliances 5Jun 15, 2013 4:15 pm 14.99 kw will be the cooling capacity not current used, most heat/cool pumps work on a 4-5 :1 ratio. would most likely draw 3500-4000 watts check the manufacturer website. 4000\240 = 16.6 amps Re: General amp requirements - common house appliances 6Jun 15, 2013 5:42 pm kassan1973 14.99 kw will be the cooling capacity not current used, most heat/cool pumps work on a 4-5 :1 ratio. would most likely draw 3500-4000 watts check the manufacturer website. 4000\240 = 16.6 amps Thanks folks. Kassan I think that's closer to the mark. The manufacturer claims a max current draw of 21 amps. Thought there must have been some magic to it, because my closest calculation came out at around 60 amps, which I knew was way to high. With the limited information I have provided, do you think a maximum 21amp A/C would run ok with a main meter box fuse of 45amps? Bare in mind I have a gas hot water system and gas stove, so that takes the load off the electricity a bit. I obviously have irons and kettles that are used occasionally, along with the tv etc... Re: General amp requirements - common house appliances 7Jun 17, 2013 3:52 pm 45 amps is generally ok, you must consider that you will very rarely if at all be using all appliances and lights etc at same time. if you have 45 amp supply and a/c using 21 you still have 24 amps to play with. 24 x 230= 5520 watts available i really dont think you will be using up all this power while your a/c is running? Re: General amp requirements - common house appliances 8Jun 22, 2013 4:11 pm kassan1973 45 amps is generally ok, you must consider that you will very rarely if at all be using all appliances and lights etc at same time. if you have 45 amp supply and a/c using 21 you still have 24 amps to play with. 24 x 230= 5520 watts available i really dont think you will be using up all this power while your a/c is running? That's what I would have thought, but then when I sat down and worked out the power requirements of common household devices, I realised I might. My oven for example is 5300 watts. It's not totally inconceivable that the A/C might be running, and I might be using the oven, and the mrs might be vacuuming with the 2000watt vacuum cleaner Re: General amp requirements - common house appliances 9Jun 22, 2013 5:03 pm We had the same sort of advice - one sparky said upgrade the next said not to. We did, under the banner of rather be safe than sorry - and cheaper to do it now rather than later. And it only cost us around $1600 to upgrade. We figured we could quite possibly be running the heating/cooling, whilst the kids have on one TV (and console) and hubby has another on. I could vacuum (built in), and have the oven and washing machine, and possibly the dishwasher all going at once. Re: General amp requirements - common house appliances 10Jun 24, 2013 4:16 am Upgrade of this relatively medium scale should not be that expensive. Around 1500$ and you will get pretty much enough 50amps You should check your detail drawings, it may show downpipe within brick pier. 14 14079 This was on google. 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