air separation location

Tom Hopkins

Will go with placing it in the primary loop. As per Siggy's book.

thanks for the input

Pete

Tom Hopkins

air separation location

Setting up primary/secondary piping for a Weil-Mclain Ultra.

Weil-Mclain manual shows the air separation/expansion tank located on the secondary piping on the suction side of the distribution pumps.

Everything I read in Siggy's "Modern Hydronics" book shows and says to put the air/separation/expansion tank on the primary loop on the suction side of the boiler pump. The way he explains the location and issues with pressure makes sense.

Not sure what to do, any thoughts?

Pete

Brad White

Location, Location, Location

If we are talking air separation, the location where water is hottest, pressure is lowest and velocities are lowest is the best spot.

If we are talking expansion tanks, the latter two criteria are most important, but especially pressure. An air separator makes it's own reduced velocity. Temperature is not a factor.

One could argue that the top of the system would have the lowest pressure (it would) but would probably not be the hottest unless it was an express riser to a down-feed system.

The fact that the suction side of the circulator is where the expansion tank is best located also makes that the point of lowest or at least constant pressure in the system (PONPC or Point of No Pressure Change) and if off the boiler, the hottest. Sounds like a good place for an air separator.

This is also why most air separators have this nifty 1/2" FPT tapping for an expansion tank. How convenient?

If I am doing P/S and using a low-loss header, that to me is the best location and most LLH's have integral air removal- it is on the suction side of most if not all pumps, (both primary and secondary), has low velocities and is at the hottest temperature, at the top where boiler water enters. By definition that is the PONPC.

Don't over-think it though.

Tom Hopkins

location will be the same

The expansion tank will be hanging of the Spirovent Jr. air separator. So location is the same.

What you are saying, I think? Is what Siggy's book tells me to do and what I was planning to do.

Just a little confused as to why the boiler manufacturer's manual tells me to put in somewhere else.

Thanks
Pete

Brad White

I do not think that

the boiler manufacturers are telling you anything radically different. What they tell you has to work, as does what Siggy tells you. I see the two locations functionally as a distinction without a difference.

Uni R_2

Why not just follow W-M's advice?

Since the boiler circ for the Ultra should be on the return, the PONC in the boiler loop will not have the hottest water and may often be cooler than the water in the distribution loop.

Furthermore, the water in the distribution loop will be circulating more often allowing the air separator to work longer.

I'd go with W-M on this one, they are the ones who have tested this particular configuration with their boiler.

Tom Hopkins

pump on Supply or return

The Ultra manual's piping diagrams show the pump on the return. So then you are right about the PONPC, hottest water temp and location of the air separator.

If you go way to the back of the manual there is a tiny paragraph that says the pump can be on the supply or return piping. I am/was planning on putting the pump on the supply side. In that case the hottest water would be on the supply side of the primary loop and the best location for the air separator would be before the pump on the supply side of the primary loop.

Not saying you or the W-M manual are wrong, just in my experience there are usually several "correct" ways to do "it".

And I'm being somewhat lazy, since I have the secondary piping done and did not put the air separator on it and would prefer not to have to cut it apart. And yes I am slightly concerned about not following the W-M manual. And hope I do not have to correct it.

Pete