你好,

感谢所有GBA贡献者在这个网站上的信息，并对Dana Dorsett为许多相关主题的技术指导从另一个论坛。去年秋天，我第一次有了房子。你的贡献让我在暖通空调更换项目上开始了正确的方向。

总而言之，我将更换我在纽约长岛的错层房子里已有几十年历史的暖通空调。我的目标是空气密封/绝缘足够两个独立的迷你分裂来处理加热和冷却-一个在楼上，一个在楼下的简单/经济配置。我使用基于燃料使用的方法(两年的冬季供暖费用)估算了供热负荷，并粗略地用I=B=R计算进行了核对。双方意见大体一致。我雇了一个著名的当地RESNET评估员，对每个房间的手册j进行评估。令我失望的是，他的预改进结果比我的估计高出大约50%。他努力检查自己的结果。

我已附上平面图和Manual J结果供审核。

我的问题,
1）基于下面的详细信息，是在两个磁头结构技术上是可行的，说两富士通12或15RLS3？需要注意的是在连接的平面图如图“头2A或2B”将被安装在内壁 - 安装是如何棘手假定距离到外部单元<35'？2）请评估所附手册Ĵ结果。与其浪费时间与此RESNET评价者来回的，我们怎么能可靠地降低他的结果的方式，对浆纱，定位头有用，同时最大限度地减少房间到室温平衡问题？3）任何人有在没有在每个级别头错层房屋迷你分裂的经验吗？我家有三个层次。我没有计划安装一个头覆盖露天楼梯，比其他单位，或者一个吊扇对流其他较低20'x20’ 巢穴。你看到大红旗在这？请注意，书房有滑动玻璃门（0.6 U）朝东75平米，楼板上档次，外墙，壁炉到南部，和到西部附车库。4）以任何机会，任何人有NY HVAC承包商不打上浆的经验吗？ All this exercise is moot if I cannot find a reliable installer to do the proposed work. I contacted many, no serious bid (one head per room, 4+ tons system, $15k+ install, etc). I found “diamond” dealers to be no better than others. The mini split option is only economically feasible for two heads. I may as well replace the beastly HVAC in-kind for cheap, and invest the difference in solar PV. I have included a lot of details below. I apologize for the lengthy post. ————————————————————————————————————————- Location: Heating and US Climate Zone 4, Nassau County, NY House: See attached floor plan. 1950s built, 2×4 framed, two-story high split-level structure. There are four levels in the house, each level occupies half of building footprint. Starting from bottom up – unconditioned finished basement, den/attached garage at street level, living/dining/kitchen 5’ above street level, and upstairs bedrooms. 1800+ sq ft excluding basement, 2400+ sq ft including basement. Master bedroom as bonus room above attached garage. Total less than 100 sq ft of west-facing windows. Existing Conditions: Heating – 1980s gas boiler, 165k btu/hr input, typical 70F indoor setting during winter, no major temp balance issue (even in bonus room, +/- 3F at worst on +15F nights). DWH – 2000s, indirect, 40 gal. Cooling – 2015 SEER 13 outdoor unit, 1970s air handler and ducts in unconditioned attic, 3-ton, 10 central ac registers throughout the house, no comfort issue on 85F days. Fuel-Use Based Heat Load: Ranging from 38k Btuh to 45k Btuh for temp range between +15F and +70F (+70F to match Manual J input, this is also my house’s temp setting) I=B=R Heat Load: Roughly 38k Btuh at pre-improvement conditions Pre-Improvement Conditions: Roughly 5” fiberglass batts on attic floor; fiberglass batts in walls; all double pane windows; unconditioned finished basement (rim joists and foundation walls not accessible without major demo); all attic floor openings are temporarily sealed with plastic film in winter (whole house fan and ac registers, etc); fiberglass batts between bonus room floor and garage ceiling. Pre-Improved Blower Door Results: 3800 CFM50. ACH50 about 13 using whole house volume (including basement) of about 17,000 cu ft. Extent of Ongoing/Planned Retrofit – Air seal as much as I can in attic and garage; remove air handler, ducts, house fan and seal/insulate all attic openings; 10” blown cellulose to attic floor; ceiling fan in each bedroom Manual J Results: See attached results using 3800 CFM50 infiltration, pre-improvement conditions at 99% design temp. – I specifically asked for aggressive analysis. He calculated 66k/38k Btuh heating/cooling loads, and struggled to sanity-check his results. His reported loads ignored unconditioned basement. – Saw some single-pane windows used – likely skylight windows. Can reduce u-value in half, or about 1500 Btu/h heat loss reduction. – 24k Btuh heat loss from “winter CFM” appears unrealistic. He could not explain how the software goes from measured blower door 3800 CFM50 as input, to 394 “winter CFM”. What is the correct conversion? (394 CFM x 55F ΔT x 1.08 ~ 24K Btuh of heat loss) Regardless, I understand blower door exaggerates leaks from neutral pressure plane. What would typically be a more realistic CFM to use for both winter and summer? – If I am removing ducts in attic, there should be no heating/cooling loss from ductwork? It reduces heating/cooling loads by 9k/5k Btuh. – Not clear if he added heat gain from four people and other equipment? This further reduces heating load. – His room-by-room cooling loads confirm there is no need for one head per bedroom, assuming I can trust his cooling load results. – Den peak loads are scary high. What’s the realistic range based on descriptions in Question 3? Please comment on my rationale blow. Without overthinking too much: – I am comfortable with my fuel-use based heat load on the order of low 40,000 Btuh at pre-improved conditions. If I understand correctly, at +17F, Fujitsu 12RLS3 covers 13,500 Btuh, and 15RLS3 covers about 18,000 Btuh. With some improvement, a combination of two 12 and/or 15RLS3 should cover my whole house head load at 99% design temp? No need to worry about minimum modulated output at +47F since my part loads are high? – If an existing 3-ton central ac with leaky ducts in attic can cool the whole house comfortably, with some improvement, a 2-ton to 2.5-ton sizing should be appropriate? – Only issues are upstairs head placement in a way that does not complicate installation, air distribution to bedrooms and den despite open stairways, and finding a competent installer to comply with intended design. Thanks to those who make it this far in my post. My family and I will appreciate any comment. Thanks, Jerry