Which side of boiler does the recirc go?

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Old 02-28-06, 08:46 PM
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Which side of boiler does the recirc go?

I read on a pretty regularly, that the recirc pump should be positioned on the feed side of the boiler (so that the reirc pumps away from the boiler).

Every boiler that I have seen (at least in the Boston area) always has the recirc on the return side fo the boiler (pumping to the boiler). This is true for even new installs.

What are the advantages/disadvantages? Was there a change in thought as to which side the recirc should be positioned on?

Just curious.
 
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Old 03-01-06, 06:29 AM
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Putting the circulator on the supply solves a lot of problems. The reasons that not all boilers are done that way today is:
1. Old timers refuse to change their ways.
2. Boiler manufacturers lure inexperienced installers with the promise of a fully packaged and wired boiler. The only way to fully package and wire it is to have the circulator installed. They can't figure out how to crate a boiler with the pump on the top so they continue to install it on the return. Smart? No. True? Yes.
Ken
 
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Old 03-01-06, 07:18 AM
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With many high efficiency modulating condensing gas boilers the manufacturers recommend the circ be installed on the boiler return side. The reason for this is to maintain pressure on the flow switch and across the heat exchanger (which can be a bit restrictive on some models).

For everything else it is normally better to have the circ on the supply side pumping away from the expansion tank (and boiler). This is to help with air elimination because the heated water is less likely to entrain air.
 
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Old 03-01-06, 06:11 PM
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Pumping Away

This is one of the finer points. There is no doubt it is better. Is it critical? In the vast majority of applications, no.
 
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Old 03-01-06, 11:01 PM
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Thanks everybody for the responses.

I did not think that having the recirc on the return would cause problems, because all the boilers (mine and others) do not have issues. I was just wondering if this was either a geographical preference or a relatively new way of doing it because it was discovered/identified that it is a slightly better option.

Sounds like it might be a little of both.

Thanks for some of the finer points for putting on either the return or supply.
 
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Old 03-03-06, 08:00 AM
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pumping away

cgar, if you are in the Boston area [I'm down on the Cape], you might have seen a recent "Ask This Old House" where Trethewy (sp??) solved an air problem by replacing the expansion tank (an old one that was probably shot) and in the process moved the circ from return to supply. The following studio segment had him diagramming and describing the principle of pumping away, etc. I didn't catch the whole thing, but that's the gist of it.

I mention this because probably five years ago he installed a spirovent on a residential project. Two years later a guy (who happened to know Trethewy from comm hvac work in Boston) installed one on our system. Said "these are really catching on."

So maybe in 3-5 years pumping away will be standard here, too. FWIW I have a sneaking suspicion that my air problems described in a thread here could be alleviated if not cured by going to a pumping away setup.

Who knew This Old House was such a fashion trendsetter?
 
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Old 03-03-06, 02:41 PM
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Unfortunately, I think "This Old House" is all the annual training some hydronic service people get. You are correct about the Spirovent or Honeywells new unit called the SuperVent. Both solve a lot of air problems. Getting rid of compression tanks is important too.

Ken
 
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