Browse Forums Heating, Cooling & Insulation 1 Jul 31, 2013 5:18 pm Hi All, Was wondering if anyone can help as I am concerned - we recently built and moved into our new double storey, we opted not to go with the refrigerated cooling and have evaporative systems (standard with package) on the upper floor, however, we're going to put in a split system inverter in our activity room upstairs for those 30C+ hot stinking days, we are in Melbourne so it is mainly DRY heat. The below is my floor plan of where I want the air conditioner to serve, it's about a approx 40m2 place, perhaps slightly more around 43m2 if we considering the little hallway and a bit of the master room where I want the air conditioner serve if possible. I have a air conditioner installer out recommending a 9.2kw system (he recommended a MHI one), however, I am a bit skeptical.... Like ⋅ Add a comment ⋅ Pin to Ideaboard ⋅ Link: http://tinypic.com/r/2l8eyrs/5 His explanation is: - 150W (CSIRO quotes 125W/m2 so I guess a little on the overkill end already) per m2 using this I get 6.450W - West facing windows/large 2 panel sliding door will be stinking hot in summer so add another 1kw. - Since hot air rises and I have a staircase right next to the activity room, he allows another 1kw for this (right beneath the activity room is the lounge room with a large West facing window). - Since my compressor will be on the ground, he will need to run the pipe up the wall (approx 5m) so that will lose some power, he adds another 0.5kw. This is how he came to the conclusion I needed a 9.0kw - closest thing was 9.2kw Fujitsu or MHI. Does this sound right? I was told by a mate who is an electrician by trade that a 7kw to 8kw split system would better serve me as he reckons 9.2kw could be prone to short cycles and suffer from premature compressor failure, but reckons JUST might be OK since it's an inverter and also Melbourne has dry heat. I've read it is better to go underpowered than overpowered if you don't get the power right. My friend did however comment that as it is an open area and that I will be opening the master room door in summer to allow for some heat relief, 9.2kw might JUST be OK. I've actually already ordered the 9.2kw MHI (non refundable from a retailer) but now thinking if it's a bad idea, I'll cut my losses and sell it off for a loss or shall I got ahead with the install? Thoughts?? PS: I also checked out the generic calculator on the Fujitsu website which recommended me a 8.0kw based on West Facing Windows and 40m2 area to be cooled - this also seemed excessive to me as a 7.1kw seemed like the right size for this area? However, when I consider the other factors such as length of pipe cooling loss and the staircase it kind of makes sense to go for a 9.2kw?? Thanks for your opinions. Re: Inverter Split System (9.2kw too large??) 2Jul 31, 2013 8:57 pm I would have put a 7kw system. See if you can swap over to a 7kw and get a refund for the difference. If not, the 9kw will be fine, but seems overkill. To be honest, wouldn't it be better to install it in the living area downstairs where people are most of the time? Re: Inverter Split System (9.2kw too large??) 3Aug 03, 2013 10:57 pm Hi You could go with a 9.2kw system though you'll find it'll probably very rarely run at full load (only on 38+ days for example). Being that nearly everything is invertor driven these days you can get away somewhat with installing an over-sized system as the short cycling is not as apparent as a DOL compressor which is either on or off. It is this start up which would shorten the compressor life is occurring frequently. There's not really a loss of power installing the outdoor unit at ground level and running pipework up the wall. It is more whether the compressor has the pumping capacity and lift to pump up the rise to the indoor unit (evaporator) and get back adequate oil return. The manufacturer can generally tell you what the maximum vertical head their system can pump up if it isn't listed in the installation data. The general rule of thumb is ~12m of lift before an oil trap is required and another trap each subsequent 7.5m of lift. I'd be highly skeptical if an oil trap was required for for what you're describing. If the pipe run is greater than the pre-charged refrigerant charge is for, it would then require addition of refrigerant to ensure the evaporator is working optimally and not starved of refrigerant. The installer should be checking this as part of commissioning of the system. hth Move your linen into laundry and access laundry from your present linen space 1 8007 consider putting in wall WC instead of robe in the same bedroom, then it might be doable to hook up to the existing piping. 4 6627 4 4490 |