Monoflo tee and pumping away
I am an installer and have been in the trade for 6 years. I was taught pumping away on boilers from the first heating season Ive ever encountered. Ive read Dan's "pumping away" book. I recently just got 2 more of his books because I loved it so much. There is a sort of debate going on at my shop between me and some other guys. I am being told that on mono flow tee installs I cant put the circ on the supply and it needs to go on the return. Reason being in the past before I was there they have installed boilers where the previous boiler had the circ on the return and they installed circ on the supply and had all kinds of "trouble". Dont get much more information than that. Kind of wanted to post to the forum and see what others thoughts are. Im known as the "pumping away" kid at the shop so this is the second time a sales person or supervisor has advised me I have to install the circ on the return for this particular install. Pros or cons? Thanks in advance!
Comments
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They don't know what they are talking about.
In most residential systems the pump location doesn't matter because the systems typically have little pressure drop.
But pumping away is better and if possible, you always pump away from the expansion tank.
4 -
just to be clear the pump could be on the return and still be pumping away as long as the expansion tank is connected at or near the pumps inlet
Many mod cons have the pump on the return to help overcome pressure drop in the boiler
Here are two examples, one with pump at return, one at supply
Typical ci boilers have low pressure drop so tank at return, pump on supply is still “pumping away”
What is important is for the air purger to be at the boiler supply out, the hottest point in the system
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream2 -
ideally you are also pumping out of the air separator so it is both highest temp and lowest pressure.
the water doesn't know if you're pulling it or pushing it, it is the same either way once you're in the system loops.
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And the behaviur of a monoflow system has nothing to do with the location of the pump nor even the static pressure in the system. It does, however, have a lot to do with the water velocity in the distribution pipes — so one way to mess it up which your guys may have found is to substitute a very different pump…
Br. Jamie, osb
Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
4 -
high pressure drop through the monoflo circuit, plus the fact radiators are in series makes the pump selection critical for it to work as intended.
Inadequate flow may leave you with cool emitters at the end of the loopBob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream1 -
If you're replacing a boiler where there's a mono flo system, its important supply and return flow stay the same. Where in a series loop it doesn't matter if you reverse flow in most cases. I've replaced numerous boilers where's there's a mono flo system and the old had the B&G 100 on the return. New installs always pumping away. Never an issue.
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I appreciate the feedback. My thoughts for why they had problems in the past was flow problems/ pump selection just like you guys stated. Just wanted to make sure I wasn't alone in my ideas/ thinking
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You're not. And I hope you are wearing the nickname "PumpingAwayKid" as a badge of honor. It's a great title to have.
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I would get tee shirts and hats with "The Pumping Away Kid" and wear them proudly.
Edward Young Retired
After you make that expensive repair and you still have the same problem, What will you check next?
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That is awesome!
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And why were circulators shipped on the return in the past? I remember reading an article that @DanHolohan wrote years ago. I believe he mentioned one reason was ease of shipping?
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I think some packaged cast boilers still ship with circ on return?
Bob "hot rod" Rohr
trainer for Caleffi NA
Living the hydronic dream0 -
Thank you for posting this.
1
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