Is \"pumping away\" only for residential systems?

Syncro

I am a big fan of the pumping away concept and have spec'ed several systems with that approach. Lately, my church needed a new boiler. The original piping was pumped on return side. The boiler only lasted 16 years before the segments started to rust (big air problems). I suggested we consider reversing the water flow for the new install - the contractor answered "that's only for residential systems". Seems like Boyle's law is the same regardless! Am I missing something? --Dale

jim lockard

Pumping

You aint missing nuthing Dale. Science and physics do not know or care how or what the building is used for, so stand your ground. Maybe shareing a copy of Dans book will make a convert of your contractor. Best Wishes J.Lockard

JohnNY

Just in case there's any confusion.....

...you wouldn't be "reversing the flow" by moving the pump.


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[Deleted User]

Correct...

ONLY if you don't understand the concepts of pumping away...

Stick with your guns. It is even more important in commerical with high head pumps than it is residentially with low head pumps, but it is proven in any case to be the correct way of doing things.

Do the contractor a favor and send him here for a free education.

ME

John@Reliable_14

Mr. Carlson invented it because of commercial problems if I remember correctly

hvacfreak

High Steel

I have never worked on an old or new commercial / industrial / institutional system that was not intended to move fluid away from the expansion vessel.

Another difference is that I have never seen " racks " of circulators ( or any " injection " piping either ). Only circulators big enough to move fluid from DC to Baltimore and back again...any connected loop or device just relies on pipe.

Manderin Hotel in Washington ( bottled water costs 15.00 )...we replaced the main boiler plant , installed large " inline "circulators ( looked like large B&G 100 ( times 1000 ) only they were Taco )...these were only for the " near boiler " piping. When we started these , they ran at 0 psi with the suction in a negative. It was easy to see that the tank line connection needed to be changed from what the " engineered " drawing showed.

6 Months later we moved the tank line to where I said it should be. Thanks to Dans books I got my 15 minutes of fame. - Mike

Syncro

My mistake

Thank you all! Am I correct that air/rust problems are related to pumping on the return side?

Also, thanks, JohnNy, for catching my slip. I, of course, did not mean "reversing the flow" - that would not change. I meant relocating the circs. --Dale

Brad White

Air and Rust

You are essentially correct that when pumping TO the expansion tank you will likely draw in air via any suction-side vent, gasket or other violation. Thing is, in that case, the rust may be on the inside of the system. Not a good thing!

Maine Doug_52

Here is a shot

of the job done in one of retired school buildings in my town. Piped P/S and pumping away.

Maine Doug_52

Here is a

pic of the P/S-pumping away job done at a retired school building in my town.

Ragu_5

Gil Carson...

I think he must have been some kind of guy! Dan acknowledges him, and that is good enough for me.

There is a retired pipefitter from Boston who lives here in Maine, and he told me 2 things: The first is that they have been pumping away on commercial jobs in Boston since the early 1960's. The second is that they have been feeding at the expansion tank (Point Of Zero Pressure Differential) or [Point Of No Pressure Change] since the same era.

Sound familiar?

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Unknown

Pumping Away - Residential vs Commercial

As is usual in hydronics this is an "it depends" answer. Boyle's law helps the older air scoops operate better, "boiling" the water at the scoop by locating the scoop at the highest temp (supply side) and lowest pressure point (suction side) of the circulator. Boyle's law is less critical when using the "Spiro Vent" type of air seperators.

Where is the dividing line between residential vs commercial anyway? You are right, Boyle's law applies to both. Some boiler manufacturers actually request the pump be installed on the return to insure high velocity through their boiler tubes to keep them clean.

As much as I recommend the boiler/purger/pump and off to the system sequence some folks still pump on the return side (it works). The absolute key here is to pump away from the THERMAL expansion tank, not adding the circulator's energy into the thermal tank but using the circulator's energy as intended - to overcome friction loss!

Caution if pumping on the return side - avoid pumping turbulent water into the boiler's heat exchanger and if the pump is oversized watch it does not overpressue the system blowing the relief valve during periods of low flow (high pressure). That can cause make up water be introduced into the system once the pressure drops and starts a nasty circle of relief then make-up.

I am merely a trainier and not an installer and am always open to suggestions (and learninig) from those in the know (the installers!). Opinion from other wallies?