Domestic hot water heat recovery: Two systems or one?
我们有一个带有多个浴室的大型脚印。动力管产品似乎是恢复淋浴废热的绝佳方法。问题是如何处理在3层房屋中相距20英尺以上的多个浴室。中央排水口很容易，可以使用一根动力管，但是热水尾部需要在到达动力管之前穿越大量的PVC管。b，b从电源管进送到从中抽出的含糊阵雨也很复杂（为了倾斜每个阵列的冷侧）。在这种配置中，使用Weissman或Buderus System Woudl，因为它也可以为散热器提供一些空间加热。
另一个选择是2个动力管，每个动力管都可以单独喂养水系统。这是对大约6500平方英尺的房屋的翻新，因此2 DHW系统的想法并不疯狂。Woudl允许天然气系统成为房屋的主要系统（也许？）简单的电动罐配置2个与之远处的浴室。
Given the cost of electricity, the likelyhoold that PV may well become power of choice, the low cost of electric tanks but hampered the inefficiency of a plain boiler – what does the math work out to be?
真的很挣扎于这个……。
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PVC排水管中的横向排水距离并不重要。由于水与PVC之间的表面积接触很小，因此很少将热量转移到PVC上。当排水管是垂直的时，水的链条并沿着排水管的内部扩散，导致表面接触为5-10倍（这就是为什么需要垂直安装重力膜排水热交换器。）
It's pretty common for the drainwater heat exchanger to be configured to feed the entire cold water distribution system in the house rather than a direct home-run to the shower & hot water heater. The output temperature of a typical 40-60% efficiency heat exchanger is at room temperature, or slightly above. In the event that another cold water tap is being used, the higher flow on the cold water side of the heat exhcanger results in a lower output temp than when just the shower is running. In practice this is rarely a perceptible problem.
但是每个房屋都有不同的限制。
Edward,
这个难题有很多动人的部分。Dana Dorsett为您提供了有用的信息 - 不必太担心水平（或几乎水平）PVC管道。
On the question of "One water heater or two?", you might want to read these two articles:
家用热水：没有完美的解决方案
热水循环循环
Martin,
Thanks for the additional information. I had read the article on circulation loops and plan that approach.
One question that is wrapped up in my earlier post is "at what point does the benefit of gas for water heat get outweighed by using a separate electric resistance boiler"
Knowing that this house (at some point) will have PV, I have it in my mind that a traditional electric boiler is not so wildly inefficient in an application such as this one (if a power pipe is used)
任何人都曾经看过这种比较（使用电管时，燃气与电气）
Edward,
When you use the word "boiler" instead of "water heater," I assume that you are talking about space heat as well as domestic hot water.
Every designer has to make their own judgment on this one. When it comes to space heating, I would always advocate ductless minisplits over an electric-resistance boiler. (The minisplits will use 1/3 as much electricity.)
当涉及到家用热水时，通常的建议（用于全电动房屋）是安装热泵热水器。但是，如果房屋有足够的空间容纳大型光伏阵列，并且当地公用事业公司在其网级合同上提供了体面的条件，则有可能提出一个很好的论点，以支持电力加热器。
Thanks Martin.
The plan is to use an indirect Gas to provide hydronic (radiator) heating as well as supply hot water needs.
The second water heater would be to serve a distant set of bedrooms (leaning against a second system at this point)
The house will ALSO have a ducted minisplit system (Fujitsu given better performance in-duct)
The challenge has been getting support to do an ONLY heat pump system. Fujitsu's top rated installer in the Boston area would not do the install. They consider the multi-head systems to be very problematic to troubleshoot and were very reluctant to move forward. They put me in touch with the regional fujitsu rep at Sweeney Rogers Geraghty who frankly was nice but not that helpful.
因此，我们以散热器作为补充/备份的大部分压缩/冷却房屋出来。这是一个大的老式维多利亚时代（9k平方英尺），尽管它将被超绝绝碎（4英寸“外部孔和茂密”），但它仍然很大。亚历山大·贝尔（Alexander Bell）将在房间里放热损失，因此我们将更好地处理需要什么，但这是我们目前的想法。
“锅炉”一词可以指英国或某些英联邦国家的饮用水供水器，有时也称为“圆柱体”。但是在北美，“锅炉”专门指的是供暖设备。用空间加热锅炉加热的水罐称为“间接热水加热器”。
因此，诸如“间接气体”之类的术语会有些混乱。
除非你分享天然气的成本&电工实习icity, there is no way to determine whether/when there is a benefit to one or the other. In eastern Massachusetts the retail price of natural gas is about $1.25/therm or $12.50/MMBTU in recent years' average, whereas electricity is about 18-22 cents/kwh, depending on your supplier.
https://www.eia.gov/dnav/ng/hist/n3010ma3m.htm
https://www.eia.gov/electricity/monthly/epm_table_grapher.cfm?t=epmt_5_6_a
At 3214 BTU/kwh that's 293 kwh/MMBTU, or $53-64 /MMBT 4-5x the cost of natural gas, if used at the same efficiency.
In an EF3.0 heat pump water heater than drops to about $20/MMBTU.
对于0.67的EF燃气热水热水器，上涨约$ 18.28 /mmbtu。
For an HSPF 12 right-sized ductless heating it's 83 kwh/MMBTU of heat delivered, which costs $15-18/MMBTU, which is not very different in cost than heating with a standard hot water heater & panel radiators.
达娜（Dana），您已经暴露了我的英国根源，没有听到我的口音！
您的数学解决方案简洁地回答了这个问题。用电煮沸水是没有意义的。