P/S question

Brad White

I suggest less caffeine late in the day, Pete. :)

I am not sure and have to think about this a bit. Firstly though, the systems are flow-isolated, flow in one not appreciably affecting flow in the other. Hydraulically speaking they still "see" the expansion tank. I know you understand this, I just wanted to stipulate that to clarify the point.

If we accept that the tank connection point is the PONPC.

I diagrammed it and do not think that it would make a lot of difference if any.

Say the system is at rest and has a static pressure of 15 PSIG with the tank in the "proper" position. Say the circulator starts and the suction pressure remains at 15 PSIG but the discharge pressure goes to say 18 PSIG. By the time the water makes it's way around again, it will be back to 15 PSIG, all motive energy essentially spent. It has gone the full route around.

If you moved the expansion tank and PONPC to the other side of the tees, that is only a couple of feet. If this had any effect, that two feet of pipe would have to negate the full DP of the circulator in that short distance. It still is on the suction side of the circulator, not far away.

The water would not change direction and the relative forces of the circulators (boiler side and system side) remains unchanged so the boiler flow will still go from boiler to system and back to boiler, with system side GPM rat-racing around.

I am inclined though to try this out by moving my expansion tank to the other side of my tees, given some spare time. :) That is the only way for me at least to test this out.

radioconnection_2

P/S question

Here's something I've been wondering about. For pumping away, the pump suction side should be after the expansion tank and water makeup.

In a properly Tee'd P/S system, the two loops are isolated from each other.

What happens when you move the pump say 12 inches from one side of the P/S tees (expansion tank side) and move it to the other side? Is the pump still pumping away?

Just curious, I've been racking my brain on this one for a bit.

pete

Empire_2

Technically,....NO

Since you moved the pump to the other side, the primary loop will only see 12 psi, due to the point of no pressure change at the exp. tank and you would loose all the increased pressure that the pump creates. Dan has a great book on this very topic called "Pumping Away". Good read. Also make sure that all of your secondary pumps, pump away from the supply tee and toward their zones. This will aid in air elimination because the secondary pump will ad it's diff. pressure to the Static fill pressure. Remember the higher pressure tends to capture air and get rid of it at the tail end of the run, through elimination devices, which are on the suction side of the pump.

Mike T.