[wmcinnes]

Originally Posted by HaZRaTTy

Well I guess you learn something new everyday, I was under the general impression any restriction of flow would cause the back pressure on your pump. That being said it could be because of the 12 hour night shift and being up for 30 but I can't wrap my head around the physics behind it and how it doesn't create it care to explain?

For the sake of me explaining this I am making up some numbers..

Pressure= Force/Area
Force= Mass x Acceleration

Lets say for 1kg of water accelerates at 2m/s2.
Force= 1kg x 2m/s2
Force= 2kgm/s2= 2N

For now lets say the area of a pipe with no recirc line is 2m2

therefore, Pressure= 2N/2m2 = 1N/m2 or 1 kPa

Now lets do the same math with a recirc line, which would actually have a greater area then a pipe without it.

1kg of water accelerates at 2m/s2 again
therefore Force= 2N

This time the area will be 3m2 because we have more piping for the recirc.

therefore, Pressure= 2N/3m2 = 0.666N/m2 or 0.666 kPa

The extra area of pipe for a recirc line creates less back pressure on the pump as proven. This is such even with the valve restricting flow from the recirc line as there is still more area from the pump to that recirc valve than there would be from the pump up to an equal point in the line with no tee'd off recirc.

My explaination might be a little confusing but it works out!