North Idaho ranch boiler sizing
n爱达荷牧场的计划即将完成。房子将在坡度上以水文地板加热为单位。将有一个天然气燃料的锅炉为地板管道提供热量和一个间接的热水器。第6区，供暖1800平方英尺的内部加上车库，阁楼R 60，板r 20，墙壁R 23吹玻璃纤维，窗户三窗格U .24。我的计算将设计热损失置于28,000 BTU/HR，使用-10F的室外温度。
第一个承包商提出了使用Lochinvar 85,000 BTU/HR输入调节式冷凝锅炉的建议。该锅炉还配备了55,000 BTU/HR输入。两者都有5：1的转弯。
I’m no boiler expert but it appears to me that they have proposed an over-sized boiler.
Before I have this discussion with them, can someone please confirm the smaller boiler will work or explain to me why they may have proposed the right boiler?
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答复
史蒂夫，
当有间接热水器时，您将获得许多不同的意见。的确，当两个或三个电器或固定装置同时需要热水时，您需要大量的BTU/H。但是这种情况是通过控件解决的，而不是更大的锅炉。当对家用热水需求时，锅炉控制可以优先考虑间接热水器区域，并忽略一段时间的空间供暖需求。不用担心 - 您的房子不会冷却。
Once the domestic hot water demand is satisfied, the heating zones can be prioritized. As I said, this is all accomplished with controls, not a bigger boiler. The 55,000 BTU/h boiler is plenty big enough.
-- Martin Holladay
The most important aspect for sizing a mod-con is the minimum-fire output relative to your design heat load. Ideally the min-fire output would be less than half the design heat load, to ensure that it can modulate almost continuously for the entire heating season. The average wintertime heat load is usually less than half the load at the 99% outside design temperature, and if the min-fire output is more than half it means that it will be cycling even during mid-winter conditions, rather than modulating.
Staying within Lochinvar's lineup the "right" boiler for your loads is the Lochinvar CDN040, which modulates between 9000-40,000 BTU/hr in, 8,500- 37,000 BTU/hr out. With a max-fire output of 37K you have a 38K/28K = 1.32 oversize factor, which is nearly the exact ideal 1.4x oversize factor per ASHRAE recommendations.
http://www.lochinvar.com/_linefiles/cdn-sub-02.pdf
See also:
//m.etiketa4.com/blogs/dept/guest-blogs/sizing-modulating-condensing-boiler
As Martin points out, even a CDN040 has as much or more heat output than the burner on a standalone tank heater, and with the water heater zoned as the "priority zone" it will have no problem managing both. With the high mass of slab radiation you will NEVER see a drop in room temperature during the tank's recovery time when the heating zone's call for heat is being suppressed.
这是您的房子，您的决定，但是由于您运行了负载号，因此无需收听承包商的尺寸建议。告诉他们负载，并告诉他们您希望它们要出价的锅炉。
Thank you Martin and Dana.
One part of my heat loss calculation that I'm not clear on is what delta T to use for the slab floor to the earth below. I figured that the slab would be 80 degrees and the earth below my R 20 foam would be 40 degrees, so I used a delta T of 40 for floor loss calculation. Does that seem reasonable?
史蒂夫，
建模热损失摇来摇去m a slab on grade is complex. The soil near the perimeter of your home will almost certainly be colder than 40 degrees F for much of the winter -- especially in December and January in winters with little snowfall. However, the soil under the center of your slab may well be warmer than 40 degrees.
有关此主题的更多信息，请参阅泡沫绝缘材料会太厚吗？
-- Martin Holladay
感谢马丁。Google搜索显示，至少我可以找到我的问题的答案。似乎使用平板平板和地球之间的40度温度差异很可能夸大了热量损失。但是一个人需要对设计进行估计。
仅供参考，链接中的经济学讨论非常过时。现在安装的太阳能现在为$ 3/峰值瓦，而不是$ 8。
In some parts of the US PV is closing in on $2/watt, 75% cheaper than typical pricing circa 2009 when that article was drafted, which makes the financial case against excessive sub-slab insulation (and the somewhat arbitrary standards of PassiveHouse) even more compelling. Of course, using reclaimed roofing EPS at 1/4-1/3 the price of virgin stock goods changes the financial model too.
By the time a new PV system installed in 2017 is at end-of-life (25-40 years) the replacement equipment will be even cheaper and more efficient. At some point even the low prices of even reclaimed insulation no longer has a financial rationale.
成功。经过一番讨论，第一位承包商同意锅炉可能较小。他规模更大的动机是减少我抱怨热水罐恢复的可能性。确实有助于将GBA上的所有好信息以及Dana和Martin的教练提供。第二次出价带有合理的锅炉。谢谢。
现在，如果我能在爱达荷州北部附近找到回收的屋顶泡沫的来源。
Oversizing the boiler for better domestic hot water performance is a common error, and rarely necessary. The "right" solution for higher hot water performance (99% of the time) is to up-size the volume of the indirect, not the boiler.
全国泡沫几乎可以在任何地方发货，并且在全国有多个仓库。（他们为博伊西的圣阿尔彭斯区域医疗中心提供了回收的泡沫。）
http://nationwidefoam.com/
您还可以联系Couer d'Alene或Spokane或Moscow/Pullman的商业屋面公司，以购买再生泡沫。我敢肯定，有人坐在一个充满回收商品的仓库上，他们愿意以一定的价格分享。