WM piping diagram from the manual.

Lil-Roc

They are correct... the pump is pumping away. At first it looks miss leading but look at the arrows at the diafram tank, in the diagram you see a tee and an arrow. On the compression tank side the tank is tapped off of a different tapping than the supply piping.

JohnNY

Page 17, Figures 9 & 10

Are we comfortable with the circulator and expansion tank placement?

CGa

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

JohnNY

Yeah, but...

they denote having the pump on the supply as an *alternate location as if first choice would be to have the pump on the return.
Sure, it's pumping away from the compression tank but it's still adding its outlet pressure to the boiler which is, of course, where the relief valve resides.

I don't like it.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

bobbyg_4

There isn't any consistency in the piping. In one they show two pumps one of them marked as "alternate". In another they show the circulator pumping towards the air separator.

Then you have this as one of their documents:
http://www.weil-mclain.com/professionals/services/Bulletins/SB0206.pdf

It reminds me of once getting into a discussion with a "now" regional sales mgr. about how in a secondary zone the circulator should be pumping away from the common piping (where primary/secondary meet). he wanted to argue with me saying it didn't matter how it was arranged....

[Deleted User]

but how is the air being sucked

into the system; ie, what 'aperture'/'opening' would the air leak into?

"Given a sufficiently high pump head in the system supply, the return pressure may become slightly negative. This can result in air being sucked into the system causing air bound loops and greatly reduced flow in much of the system piping leading to poor heating"

Unknown

I thought

as long as you're pumping away from the expansion tank , it makes no difference where the circulator is mounted ?

Steamhead (in transit)

It can

if the tank connection is on the return and the circ is on the return, pumping away from the tank but into the boiler, the pressure increase in the boiler when the circ starts may cause the safety valve to open. Dan's book has it right.

The diagram with the plain steel tank hooked into the built-in air separator is fine, as long as the circ is in the "alternate" location.

To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"

[Deleted User]

Dan's book has it right.

which book/page?