08-19-13, 07:40 PM | #11 | |
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The questions are fine, I'm looking for advice. First, I built the house around 20 years ago. Oil heat, radiant tubes in the floors (6 x 200 ft. loops and a loop for the new room that isn't in the system yet). 100k boiler at 110 to 120F into the radiant. I have a nice Tulikivi soap stone fireplace/bake oven that can carry the house in the winter if I need it too. I originally thought about using the mini split for just the new room which adds about 225sq./ft. to make the house about 1800 sq./ft. but now I'm thinking I may try to go further. I thought about a deep well heat pump system that would cost me about 15k before rebates (2 to 3 ton) but I don't like the idea of running on electric either. First, I won't know till the spring how much I'm getting out of my added intertie/off grid this summer (added 4.2Kw to already 6.4Kw intertie). Right now (summer time) I'm making about 1 MWH, give or take, after my usage. So ideally I guess I'll have to go with oil partially this winter to see what the figures show. Also, hopefully, I'll get a windmill or two up this summer and maybe a micro-hydro into the stream. The house is well insulated and tight and the sun room I added a few years ago, helps when the sun comes out, even in the winter as it's on the south side of the house. Rob . |
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08-19-13, 07:48 PM | #12 | |
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I have a pretty good weather station here as I monitor the wind data in my front field, yes, just before dawn is usually the coldest. Rob |
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08-21-13, 02:29 AM | #13 |
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If ultimate low temperature performance is what you're after, using an air-source mini-split, two lines come to mind:
1. Fujitsu Halcyon 2. Mitsubishi Hyper Heat Of the two, the Mitsubishi boasts better heating numbers at low temps, favoring capacity over COP. It claims full rated capacity down to 5 degF and 70-75% of rated capacity at -13 degF. Can you say "hyperspeed compressor engage"? For a boiler "replacement" unit, the Mitsu Ecodan system has been in widespread use in the UK for years, and has been well documented to meet demand down to -20. Last edited by jeff5may; 08-21-13 at 03:00 AM.. Reason: links |
The Following User Says Thank You to jeff5may For This Useful Post: | Robaroni (08-21-13) |
08-21-13, 06:08 AM | #14 |
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i need to find the test paper that I read but it says that the Mitsi numbers are not as good as they claim and are roughly on par with the Fujitsu and Panasanyo will be coming out with something much better shortly so there may be some competition. That said, it seems the holy grail would be to have one of these inverter units doing floor heat but we don't have the market yet to get the good stuff over from Europe. Damn scorched air.....ruined everything...LOL.
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08-21-13, 06:44 AM | #15 | |
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As far as radiant heat - no noise, maximize space, house runs cooler but feels warmer, no radiators .... As far these commercials showing babies on a warm floor, if your floor is that warm you're melting candles! Rob |
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08-21-13, 11:21 AM | #16 | |
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I'm personally looking at a 1 ton for cooling and the 13500 BTUhr at 17f of the Panasonic unit is actually enough to heat my house at 17f although the temperature might sag a bit when the unit defrosts. If I were to close the door and only heat my bedroom with it and let the rest of the house get cold it would likely cost very little to run in total heating cost in comparison to straight natural gas. 1 ton cooling will cover a 10 degree drop versus the outside temperature with no glass shading, so an 88 degree design day would have the house at 78 degrees which I can live with for the efficiency that these units provide and I'd likely give them a good head start cooling down to 68 degrees to get them ahead of the game and burn off humidity and then the mid/high 70's won't feel too bad. Worst case, I still have the oversized 8.5SEER 22,000 BTU beast to fill in the gaps in case the mini-split falls too far behind but I have a feeling I'd only be motivated to kick it on for 2 hours or so when we hit temperatures in the 90's while having others at the house and I'd still make sure the mini-split was taking the brunt of the load. Adding shading to the glass will likely make a 1 ton perfectly capable of covering the entire load as 10,000 BTUhr would cover more than 30 degrees difference of heat transfer through insulation and infiltration. Right now it seems that about 30% of my cooling is due to solar heating through the glass so I really need to cut that back. .75 ton units --- Panasonic CU-XE9PKUA Cooling 8700BTUhr 16.1 EER, 28.5 SEER Heating 12.5HSPF 12,000BTUhr at 47f and 10,600BTUhr at 17f --- Fujitsu AOU9RLS2/ASU9RLS2 Cooling 9000BTUhr 16.1 EER, 27.2 SEER Heating 12.5HSPF 12000BTUhr at 47f and 7300BTUhr at 17f --- 1 ton units --- Panasonic CU-XE12PKUA Cooling 11,500 14.35 EER, 25.5 SEER Heating 12HSPF, 13,800 at 47f, 13,500 at 17f Fujitsu AOU12RLS2/ASU12RLS2 Cooling 12,000 13.8 EER 25 SEER Heating 12HSPF 16,000 at 47f and 9700 at 17f Last edited by MN Renovator; 08-21-13 at 11:31 AM.. |
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08-21-13, 11:35 AM | #17 | |
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Apparently those are in service now though, they have 12 stages of capacity(20-130% nominal). Water flow is variable speed too. "Up to a 5.3 COP and 41 EER rated at 50% of capacity, even at stage 10 of 12(roughly 80% of capacity) the unit takes 2200 watts to operate the flow center, blower and compressor to heat the 3000 sq foot home this was installed in" http://hvac-talk.com/vbb/showthread....rnace-7-Series Last edited by MN Renovator; 08-21-13 at 11:38 AM.. |
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08-21-13, 06:02 PM | #18 |
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MN,
I see your point about COP at sub-zero temps. With air-source units, there's no escaping the cliff at or around 20 degF. Either the unit loses heating capacity at slowly declining power draw or you increase power draw to maintain capacity. No two ways about it. It looks to me like Mitsu fielded too many complaints from customers about their units not producing "hot" air in frigid outdoor conditions. With the hyper heat models, they went the way Hallowell did, increasing mass flow at the expense of COP. When outdoor temps take a dive, they "over-rev" the compressor to keep up first, then do something proprietary and secret with the multi-split units("hyper-rev" compressor? Flooded evap? Suction line hx? AUX heat? Anyone...anyone??) when it gets really cold. So now Joe Dirt or Joe Six-pack can't complain about Mr. Slim not keeping their trailers warm during the winter. They might pay 200 dollars a month more for that heat, but guess what? The dag nabbin thing does what it should when it's freezin outside. Fuju and Panyo have chosen to try to maximize COP at the expense of sub-zero capacity. With larger outdoor coils and inverter compressors, they may over-rev a little, but not enough to injure efficiency. At Rob's -20 temps, they may only put out 1/3 of rated capacity, albeit at decent COP. To meet this condition, expect to spend double on an oversized unit that would then run at reduced capacity in milder weather at near water-source efficiency. Either way, which unit to go with depends on the end goal. For a 225 sqft room, a 12k hyperheat or 15k rls2 would meet the need at -20f. For around 2000 dollars max. Last edited by jeff5may; 08-21-13 at 06:11 PM.. |
08-21-13, 07:01 PM | #19 |
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Jeff,
Thanks, I have one option I didn't mention. When it's 0F and below out I can close that room off. I won't get to play with my 'toys' in it but eventually it will warm up outside! Rob |
08-21-13, 08:44 PM | #20 | |
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I'd be careful with the numbers supplied by ARI as it seems they don't take into account all the ancillary loads such as floor heat pumps or Desuperheat pump (sometimes). It has always been that way, IIRC. |
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