Replies

1. Expert Member
   Dana Dorsett|Jan 15, 2018 12:15pm|#1

   If you put the return at the ceiling level and the supplies are at the ceiling level it will just short-circuit- all the flow would be happening in the upper 2-3' of room air, which is the opposite of what you're looking to achieve.

   除非有相当紧密的苏之间的门pply registers and the stairwell to the upstairs there is probably already adequate return flow paths. If not, converting partition wall stud bay into a jump duct, with a grille near the floor on the room side, and another near the ceiling on the side heading toward the return path/stairwell, using the stud bay as the duct between them removes the coldest air in the room (near the floor) rather than the warmest air (near the ceiling), which will improve the overall mixing.

   Installing narrower duct boots and register grilles designed for maximum throw would increase the exit velocity to achieve better mixing.

   If all else fails, low-temp panel radiators running off the hot water heater could heat those rooms.

2. GBA Editor
   Martin Holladay|2018年1月15日01:50 PM|#2

   J. Cryder,
   When a forced-air system has fundamental design issues, the fix isn't easy or cheap. In your case, your supply registers should have been installed in the floor instead of the ceiling, and each of your home's two floors should have had its own zone (and its own thermostat).

   您的问题类似于其他GBA读者最近发布了类似问题的人：如何预防/缓慢升高楼梯间？

   Fixing the problems of your forced-air system would be expensive. It would probably be less expensive to install a new ductless minisplit unit to provide downstairs heat.

3. Expert Member
   Dana Dorsett|Jan 15, 2018 03:18pm|#3

   Also note:

   "The good news is that the air handler is powerful. In the summer it cools the whole duplex in 15 minutes with the AC."

   这实际上是坏消息，因为它意味着AC（和可能炉子）对实际负荷进行了荒谬的超大，这导致效率低下，并且在作为单个区域操作时的楼层温度分层（这是您目前的情况。）

   它实际上是一个区域吗？（我猜“是”）

   Where is the thermostat located?

   If the thermostat is upstairs and the heating cycles are short it hardly matters what the flow rates are- there isn't enough continuous air exchange to overcome the temperature stratification. Ideally you would have a right-sized furnace, that would take more than 15 minutes to satisfy the thermostat even with a narrow differential setting on the thermostat, that would run nearly continuously, at a 75% or higher duty cycle to keep up whenever the temperatures were below 20F.

   Using the nameplate efficiency of the furnace it's possible to use wintertime fuel use against heating degree-day data to measure the heat load, and compare it's D.O.E. output BTU to the calculated heat load. There will be some error due to the large difference in temp between floors, so use base 60F rather than base 65F degree-day data to compensate for that. Details on how to do that can be found here:

   //m.etiketa4.com/blogs/dept/guest-blogs/out-old-new

   A typical 1800' brownstone might have a heat load at +15F outdoors (NYC's 99% outside design temperature) and 70F indoors of about 35-40,000 BTU/hr, and a cooling load of ~20-25,000 BTU/hr. If the fuel use heat load calc comes up substantially higher than that it's probably due to high air leak rates and the higher stack-effect drive of building with 12' ceilings, and 13-14' per floor rather than ~10', and those CAN be corrected.

   If the AC is cooling the space in 15 minutes after being left off all day on a sticky July you're probably looking at more than 5 tons of air conditioner, probably more than 6 tons, but go ahead tell us the model # or the nameplate BTU numbers for the cooling coil on the air handler.

   If I had to guess the furnace is probably more than 150 BTU/hr too, and operates at no more than a 20-30% duty cycle even when it hit's 0F outside. But read the nameplate BTU in/out, and compare that to the fuel use heat load calculation.

   即使它是“只有”3x超大（足够的BTU，以便在外面的-100f时保持地方70F，它会在下次冰河时代可能发生在可能的情况下？:-)）单独的低占空比足以创造一个大量的楼层 -地板温度不平衡。

   ASHRAE recommends no more than a 1.4x oversize factor from the load at the 99% outside design temperature. So if the load comes in at say, 40,000 BTU/hr from the fuel use calculation, the largest furnace that you should be installing should be 1.4 x 40,000= 56,000 BTU/hr out. A condensing 60K-in/57K-out 95% efficiency furnace would be the "right" choice.

   If the place leaks air like a sieve or has only leaky single pane windows the load could be in the 50-55K range, but the right solution there would be air sealing and adding tigth low-E storm windows. But even a 55K load @ +15F only calls for no more than a 1.4 x 55K= 77K-out (say, an 80K-in condensing furnace) to provide the higher and more comfortable duty cycle.

   At a 1.4x oversize factor for the load at +15F the place would be fully covered for 70F indoors down to an outside temperature of -7F. Temperatures below -7F do happen in NYC, but not more than a handful of times over the lifecycle of a furnace, and when it does it doesn't STAY that cold for very many consecutive hours.

   So, start figuring out the load and the equipment capacities and report back. At some oversize factor (say, 5x) it could be that the right thing to do is to replace the equipment. But in the meantime moving the thermostat down stairs and throttling back flow to the upstairs (within limits) and opening up return flows paths near the floor level downstairs might get you to a livable compromise, if it appears gross oversizing is a primary or strong secondary factor.

4. 
   jcryder|Jan 17, 2018 11:47am|#4

   谢谢to both Dana and Martin for the comprehensive responses. I have a science background (doctorate) and I think I need a translator for much of this. I will read the other metrics off the furnace shortly, but you (collectively) guessed right --my furnace is under powered (56000btu) and the kitchen is at the end run of the system so this combined with ceiling registers (and ceiling fan) is grossly inadequate. Installing supply lines at floor level and a return or two in the first floor would be messy and expensive.

   Is there a ductless minisplit unit you could recommend size/brand wise? The downstairs is 900 ft2 but again, 12 ft. ceilings equate to over 10000 ft3. Of course, I don't need to heat the stratospheric portion of the floor. I had a quote for a unit that would be over 6K. Are these expensive to run? We are only in the unit early evening to early morning so I would not have to run it continuously.

   有趣的是，一个建议的保温家伙，因为你所做的那样，我在热水器里跑了几个水培墙的面板，他说很少有HVAC家伙会同意这一点。他是对的。我问过四个，他们不会这样做。他们说，没有足够的热量来自HWH（140）到热量，并且泵/和饮用水与加热水的混合是问题。我甚至不知道这是第5个世界纽约市的代码。

   谢谢for your wisdom.

   JCRyder

5. 
   Tom May|Jan 17, 2018 12:08pm|#5

   Got ceiling fans?

6. 
   jcryder|Jan 17, 2018 12:20pm|#6

   Yes, I have two ceiling fans in the downstairs at both ends of the floor and another at the top of the stairs to drive warm air down (from related posts this may not be effective). I did find the quote for a ductless mini split , actually less than 4 K (I was wrong). I've pasted it below and wonder if the specs are appropriate for one floor of 900 ft2.

   Fujitsu Duct, 9,000 BTU, 27.2 High Efficiency Seer
   Heating down to -15 degrees -- Advanced Comfort
   包括50英寸线设置管道，纤细的管道1管盖，带排水管的冷凝泵。
   $ 3,800
   冷凝单元将设置在钢通道上。
   Electric not included.
   7年压缩机，5年零件和1年劳动力。

   富士通管道，9,000Btu，16位效率见
   加热至+14度。
   Includes 50’ line set piping, slim duct pipe cover, condensate pump with drain line.
   $3,200
   冷凝单元将设置在钢通道上。Electric not included.
   7年压缩机，5年零件和1年劳动力。