Central air died…
Hi,
My Central air unit just died and I’m trying to decide what is best in replacement. My houses is 2 floors a 2038 sq ft with 2 zones. I’m in zone 5a in CT.
I’ll also be starting a house remodel soon and adding some more space (approx 400 sq ft) and a new roof.
我有一个燃油炉，有一些生命留在它上面。
Should I consider a heat pump at this point?
Thanks
布拉德
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Replies
>“我应该考虑一下热泵吗？”
Probably. Oil pricing is low right now, but it's volatile. Not many years ago when #2 oil was $4./gallon, even at CT's high electricity pricing cold climate heat pumps were a no-brainer investment with a fairly short "payoff".
Since you have a heating history on the place, run a fuel-use based load calculation to estimate the design heat load:
//m.etiketa4.com/article/out-with-the-old-in-with-the-new
如果您在普通的填充服务中盖上计费单上的“K-Factor”，则几个冬季填充k因素将是足够的信息来播放球场。
Depending on the particulars of both the new and old space, and how much older exterior surface the new stuff is displacing, adding 400' can sometimes even LOWER the total heat load.
如果您保持燃油燃烧器并使用相同的管道进行加热和冷却，它可能会限制热泵尺寸，可能强迫它超大。但有足够的信息，我们可能会弄清楚最好的妥协。
How many tons is the (now dead) existing AC?
Hi Dana,
My dead unit is a 2 Ton Trane.
I had a sales person here to get an estimate on a new unit and brought up heat pumps and he said he wouldn't recommend it for my area because when temps are below freezing I'd still have to resort to oil. I think I've read in the past information against his statement.
I'll look for my oil delivery slips to see if I can get a k factor.
I'm keeping the oil burner for now as I think it has life left and yes I use the ducts for both heating and cooling. I wish I had the finances to take it all out an go with mini splits but at this time I don't.
我不希望油价留在1.38美元上我买了它。
>“我的死单是2吨三角形。”
2吨富士通Aou / Aru246RGLX在典型的CT设计温度下大约22-24,000 BTU / HR，但您可能正在查看30k，给予或采取的设计热量负荷。2.5吨可能会切割它（带剥离热备份），但您可能正在查看该系列中的3吨，如果只用一个单位进行所有区域：
https://neep-ashp-prod.herokuapp.com/#!/product/25350
https://neep-ashp-prod.herokuapp.com/#!/product/25351
https://neep-ashp-prod.herokuapp.com/#!/product/25352
2吨仪调制到5400 BTU / HR @ + 47F，如果它分为区域，这是一个不错的低端范围。2.5和3笔茄子只滴回9200 BTU / HR，如果区域很大，这仍然很好。
Whether a slim-ducted mid static air handler has enough cfm to work with your fossil burner remains to be seen, but probably not.
There are others.
>"I don't expect oil prices to remain at the $1.38 I bought it last."
Probably not. The 10 year average residential #2 oil price in CT is about $3/gallon:
https://www.eia.gov/dnav/pet/hist/LeafHandler.ashx?n=PET&s=W_EPD2F_PRS_SCT_DPG&f=W
CT电力的平均零售价格已运行18-19美分：
https://www.eia.gov/electricity/state/
假设炉子上的燃烧效率为85％，每加仑提供0.85 x 138,000 Btu / gallon = 117,300 Btu / gallon，因此需要（1,000,000 / 117,300 =）8.5加仑，以提供一百万的BTU（MMBTU）。价格为3美元，价格为25.5美元/ mmbtu，以及运行空气处理程序的一些电力，可能更接近26-27美元/ mmbtu。$ 1.38 / gallon它更像是13-14美元/ mmbtu，加入了电源。
A modulating ducted mini-split will hit it's HSPF numbers in a CT climate if not grossly oversized/undersized. Assuming an as-used HSPF of 10 (= 10 BTU/watt-hour, or 10,000 BTU/kwh) it takes (1,000,000/10,000 =) 100 kwh /MMBTU which at 19 cents /kwh is $19/MMBTU.
That's a significant discount from the 10 year average price for oil, but considerably more than your recent nearly record-low priced fill-up.
屋顶太阳能发电比现在便宜residential retail price in CT, and with federal state & local incentives can be substantially lower. Even Tesla's low-risk low-money down RENTAL solar comes in at around 13-14 cents (available in CT only for Eversource Energy or United Illuminating Company ratepayers:https://www.tesla.com/support/energy/solar-panels/learn/subscription-solar) At the Tesla rental solar price a decent heat pump solution is already operating-cost competitive with $1.38/gallon oil, if you have enough optimally oriented roof area to cover most of your heating energy use.
I've recently been pitching a heat-pump + Tesla solar rental solution to an in-law in MA who has recently been paying close to 29 cents/kwh, and heating with electric baseboards. She doesn't want the encumbrance of a potentially cheaper solar lease which are a PITA to transfer to new owners, or taking the upfront hit to buy, since she's planning on retiring and moving out in less than 10 years. The severance fee to Tesla to just walk away from the rental deal is only $500, but the contract is easily transferred if a prospective home buyer wants to keep it (or buy it out and own the solar), much less messy than most solar leases. The rental costs $50/month for the 4kw system increasing by $50 per 4 kw increments in steps to a max system size of 16kw.
Give what I understand about the electric rates in CT it seems unlikely that a that twenty plus cent a kilowatt electricity and today’s low oil prices that the financial case for a heat pump could be made.
我说抵制安装更大的AC单元的冲动。一个超大的单元不会足够长，控制你家中的湿度你最终会冷，潮湿不是一个好的康卡。如果您的旧单元在最热的日子的下午骑自行车，那么它可能很大。
沃尔塔
我在这里的销售人员推荐了一个3吨三角形14个Seer单元型号RX410A。
He gave me a printout of a manual J. He didn't actually go around measuring windows and doors. Just took the sq footage of the house. I've attached a screenshot of the document.
Is this the right way to do a manual J or more of an estimate?
>"He didn't actually go around measuring windows and doors. Just took the sq footage of the house. I've attached a screenshot of the document.
Is this the right way to do a manual J or more of an estimate?"
If he didn't measure anything, the Manual-J is crap. He just entered some numbers until the tool spit out something he found "reasonable".
运行燃料使用负载计算并将其与41K热负荷估计进行比较。即使是+ 5F，这可能是99.6百分位的温度箱，而不是第99位，这已经是尺度的拇指。即使使用99％的垃圾箱通常具有较好的侵略性手册-J的余量。BridgePort Sikorsky Airport的第99百分位的融合箱为+ 15f，而不是+ 5f。
Most homes in New England have a square feet per ton 1% design cooling load of about a ton per 1500', so your actual cooling load is probably less than 1.5 tons, and a non-modulating 3 tonner would be simply ludicrous.
Take a look at Allison Bailes' graphic of square feet per ton on REAL Manual-Js, plotted against house size:
//m.etiketa4.com/article/manual-j-load-calculations-vs-rules-of-thumb
https://beta.greenbuildingadvisor.com/app/uploads/sites/default/files/images/bailes_graph_for_manual_j_blog.preview.png.
请注意,大多数的家庭都在炎热潮湿的utheast, not New England. Even there a typical 2000' house would have a design load under 2 tons, and only the very WORST performing houses in that size range would need 3 tons.
我认为你的房子不是布里奇波特的最疯狂的房子（是吗？）。
Before it croaked did the 2 ton Trane keep up with cooling loads even on days well north of 1% outside design temp of 85F?
另请注意，承包商使用的100F设计温度，而不是实际1％的设计温度。在打印报告中写入“手册-J”与实际操作的“手册-J”与手册中的实际相同，（或者是呢？:-)）完全废话。
Am also in CT 5a (10 miles inland from LI Sound). For those of you who may not know it, much of CT is a SWAMP. Humidity all summer (except when the wind blows from North) and damned cold in the winter. With that said, consider any number of low temp heat pumps and consider PV panels on the roof. My $0.02 is that oil heating is dead. Or should be.
Lastly, find your local HERS (Home Energy Rating System) and have them do an independent review (Man J) of your home. They might get you some rebates and perhaps point your to a more efficient heating system.
嗨大卫，
你有一个低温热泵的例子吗？
I would love to go to PV and a heat pump but I'm not sure financially I can do that at this point. That's most likely 30k on top of what I'm already hoping to do with a small addition.
我也距离李的声音约有10英里。
好的 - 没有销售人员，但你收到的打印输出可能是你的邻居房子和你的。窗口尺寸，太阳能取向，绝缘等所有数字都进入一个适当的人J.让自己成为专家;廉价的钱。通过减少eversource账单，应通过节能的节能支付光伏面板。
Your cheapest option is probably a new compressor, which MIGHT be able to use the same A coil your current AC compressor was using. If the old compressor burned out, it probably contaminated your refrigerant lines in which case you probably don’t want to reuse that A coil since it’s probably cheaper to replace it than flush it (but ask your contractor). You would absolutely want an R410A unit, and you would need to make sure your existing A coil can handle the higher pressures involved.
也就是说，我同意DANA，热泵是一个更好的整体选择，尽管初始安装成本更高。您需要通过数字来查看您想要的方式。
Solar doesn’t have to be as expensive as you might think, and it will shave off load from your electric bill at the same time you need your AC the most. You DO NOT need batteries — you need only panels and a grid-tied inverter. Don’t try for net zero, try for “peak shave” — size your system to offset your AC load during the day, plus a little extra. If you have a good sunny area for the panels, you can cancel most of your AC costs out with the solar system. I worked out that I can buy the parts to install a smallish solar system (around 3kw or so) for about $1/kw, which I think is a pretty attractive option. For me, such a system will have a 3-5 year payoff and that is without any gov’t incentives.
You could potentially put in a solar system and a new AC now, or a heat pump now and solar later, or any combination you choose. Solar is expensive if you go for a huge net-zero sized system or an off-grid system. If you size your solar system for peak shave only, it’s not very expensive. You basically size your system for the most bang for the buck doing this. If you can get a “time of day” electric rate (which is what I do) the solar output will shave load off during the peak time of the day (11am to 7pm for me, weekdays), so your solar system is putting out the most power during the time of day with the highest electric rate which gets you the maximum benefit. The time of day rates have lower per-kWh rates during off-peak hours (7pm to 11am weekdays, and all day on weekends, for me). I’d consider the solar system if you have a good place to site it.
账单
我认为我会因为所有有用的答案而更新这个问题。
The issue with the AC unit was actually just a bad capacitor. I got a 2nd opinion from a another company and that was the result. The unit has worked fine since the capacitor replacement and it costs me $150 and not $8k.
I will explore the option of a heat pump more so I'm ready to make that decision when the system does fail.
Thanks to all.
这可能是一个糟糕的电机运行或电机启动电容。这些零件可能是5-20美元，在需要时非常容易更换。这些电容器的典型预期寿命约为5年，但它们持续更长时间并不少见。
笔记that sometimes premature capacitor failure can occur due to compressor operation on lower than normal line voltage. This can SOMETIMES be helped with the installation of a "hard start kit" on the compressor, which is usually around $50-100 or so. Another thing to check is to make sure you have properly sized power cabling to the unit from your electric panel, and no loose or corroded connections along the way. Make sure to include a check of the contactor that operates the compressor motor.
It's easy to do voltage checks, but contractors will sometimes skip this step. It's a good idea to check to be sure there is nothing going on that will result in the same failure down the road.
账单