Expansion Tank Location

aemeeich

Hi all,

I'm looking for some advice as to where to pipe in the expansion tank on a system I'm designing.



This is an oil to gas mod/con conversion, however, the homeowner wants to leave the oil boiler in place as a backup / or to use if oil becomes cheaper (like that'll ever happen again - but who knows).



The air scoop is located elsewhere in the system on existing piping near the oil boiler connected to a compression tank.  The compression tank will be removed and I was going to leave the scoop where it is, and put in an auto air vent in the top.  This system has never had air problems, so I don't think having the scoop on the supply will be a problem.



There is not enough room to hang the expansion tank from the base of the scoop in its existing place.



I am wondering where the best location to pipe in the the new expansion tank is.  I know proper practice is to have the tank on the suction side of the pump.  I attached two photos with different ideas I have.



The first one has the expansion tank piped in right before the pump.  But the piping would have to go up and over the Knight to get to the expansion tank.  I would put a manual air vent at the top of this pipe so that the air can be purged from the line and make sure the diaphragm is kept wet.



The second option has the pipe for the expansion tank piped in a little farther upstream of the pump on the return drop.  This would allow for the line to purge out air on its own.



So any suggestions on to which way is better?



Also any comments on the design/spacing of the mixing manifold would be appreciated too.



Thanks for your comments.

Michael

Big Ed_4

Duel Units

You should be looking into piping the two units primary secondary piping and move the air scoop - expansion tank down stream of the teed in boilers (6' between tees of the same unit)and before the circulators on the supply . Each boiler would have it's own circulator to feed the manifold ...



Duel fuel is the way to go... Yes gas may rise again ...

Mark Eatherton

So long as you're pumps ALL pump away from the expansion tanks connection

it doesn't matter much where it is. Both of your drawings have the pumps pumping away, so again, it does not matter.



Ideally, the PONPC and air separator should be in the same spot, but if you are using an MBR, I don't think it much matters as long as the MBR is not immediately down stream of a pump where bubbles would be small.



ME