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baseboard btu per hour sizing

asked 2022-05-06 08:47:51 -0500

TheEnergyTutor's avatar

updated 2022-05-09 11:18:16 -0500

Does anyone understand where I can find the btu per hour size calculated by Open Studio?

The size it reports is 0.46 gpm, but this is meaningless because there are lots of different heaters out such as single pass or two pass that produce more or less heat with the same exact flow rate. Additionally the fins per inch and size have effects on the conversion of GPM to BTU/H.

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I noticed an old post says people agree that this "autosize" is not reported and should get fixed:

This post also illustrates the problem

I've read through tons of literature is there is nothing about the AVERAGE air temperature. All Baseboard is sized by entering air temperature of 65. See below. Where would I find the existing air temperature? This is nowhere.

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It seems as thought it's doing 105.67 btu/hrF * 65degF to get the 6.89 MBH. The 65 deg seems to be calculated using average water temperature (160 to 130 = 145)- average air temperature of 75 (90 outlet air from 60 inlet air). But I'm not sure where it gets these air temperatures. I can't find any literature to verify that finned tube outlet air temperature is 90 degrees, and nominal air inlet is 65 so i'm even further confused.

unfortunately open studio results doesn't even show the UA size so i have to use EPlus Output.

This may seem simple because this room isn't provided directly with tempered ventilation, but other rooms have tempered ventilation which complicates things and it is not obvious what the sizes need to be for the baseboard.

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answered 2022-05-11 10:27:13 -0500

You can find this information from the input/output reference manual and the specific formulas used are in the engineering reference manual: https://energyplus.net/documentation

Here is an online version from Bag Ladder Software:https://bigladdersoftware.co...

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I've read all that it's not helpful. I'm guessing you don't understand it either or you would have answered my question directly instead of indirectly.

TheEnergyTutor's avatar TheEnergyTutor  ( 2022-05-11 10:42:36 -0500 )edit
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@TheEnergyTutor it's helpful to describe what you've already tried (like reading all the EP documentation) per the Help page, so people that are trying to help you don't waste their time suggesting something you've already tried (rather than being impolite, ungrateful, etc.).

MatthewSteen's avatar MatthewSteen  ( 2022-05-12 16:16:59 -0500 )edit

My question is simple and clear. There's no need to explain 30 years of training and education that prompted the question. It simply would be a distraction and counter productive. There are several postings about this same exact subject, which I referenced; which all paint a fundamental flaw in this item. It needs to be addressed either via a clear explanation or modify the report. I am not alone in raising this issue.

TheEnergyTutor's avatar TheEnergyTutor  ( 2022-05-12 20:32:18 -0500 )edit

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Asked: 2022-05-06 08:47:51 -0500

Seen: 149 times

Last updated: May 11