## Parallel resistor formula

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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

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

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

Those are exactly equivalent operations!

Jim

Until Black Lives Matter, we do not have "All Lives Matter"!

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

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

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.)

If you don't know my whole story, keep your mouth shut.

If you know my whole story, you're an accomplice. Keep your mouth shut.