Parallel resistor formula

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#1
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Lets say I calc the R of the walls, the R of the ceiling, the R of the floor, and the R of the windows. A bunch of resistors in parallel. Do I need to calc 1/Rtot = 1/Rwall+1/Rceil+1/Rfloor+1/Rwindows? Or can I solve BTU=hrs*sqft*degF/R for each surface and add up the BTUs? 

 

Imagecraft compiler user

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If you can get to the equivalent  unit of Current Flow, then you can just add all those 'leakage' paths.

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I presume you are trying to calculate heat loss.    What on earth does this have to do with parallel resistors?

 

As a silly question.    Would a professional heating engineer really use BTU, degF etc ?

 

If you want to "equate" a heat loss with an electrical unit,  you would probably compare with current.

e.g. current leaving a node is the sum of the currents in the exit branches.    Your "boiler" is the current source on the entry branch.    The loss coefficient would be a conductance.

 

I can understand the use of Imperial units in your non-technical daily life.    Would a modern day American student learn about SI units?

 

David.

Last Edited: Sun. Jan 8, 2017 - 10:11 PM
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Those are exactly equivalent operations!

 

Jim

Jim Wagner Oregon Research Electronics, Consulting Div. Tangent, OR, USA http://www.orelectronics.net

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 really use BTU, degF etc ?

The average American uses 'F.

I use both 'c and 'F, as both an Engineer and a Physician.

In the Emergency Room, and elsewhere in the hospital, 'C is used.

 

When I purchased a new gas furnace ("boiler") a few years ago it was rated in BTU's.

I also think air conditioning  units are also labeled in BTU's, (in the USA).

 

BTY, Bob, Spark Fun now sells a FLiR camera kit.

I really want to play with this device, but there just aren't enough hours in the day.

https://www.sparkfun.com/products/13233

 

You could add a micro and a GLCD display and take some nice thermal images of your house, see the thermal losses, etc.

 

JC 

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I have the FLIR ONE smartphone attachment. It does an amazing job.  FLIR is supposed to release a FLIR ONE PRO, and also a 3rd generation version this year.  All of these less expensive than the sparkfun kit!

 

Tom Pappano
Tulsa, Oklahoma

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And, for a clear explanation, https://youtu.be/D-TXgj2wZOQ

 

(Though he uses the "times over add" formula rather than adding up the conductances like I always do.)

 

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