John Siegenthaler modulating multi boilers article

Ted_9

I read this in Engineered Systems Magazine. I especially liked since it was the only article in the mag that I understood.

Anyone care to discuss?

I'm not sure I understand why the circ on the return is ok in this instance.

Dan Foley

Article

Ted,

Can you post a link to the article? I have not seen it. -DF

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kevin coppinger_4

If it is a multiple boiler set up.....

and there is a primary loop, to put the circ. on the return pumping toward the boiler and away from the expantion tank is the prefered set up...even though at first it might not seem that way. I Have not seen/read the acticle but from other diagrams I have looked at that was the reasoning. kpc

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Ted_9

John Siegenthaler modulating multi boilers article

kevin coppinger , yes thats sounds right.

I scaned the boiler piping schematics. Check them out.

I know its not new since I've piped MZ's like this, but it was a nice article.

Im not sure if its online for reading?

DanHolohan

He's pumping away from the common piping,

which is the point of no pressure change for the boiler circulators. It's correct.

Ted_9

OK i get it now.

Robert O'Connor_3

Modulating Multiples

Try this:

http://www.esmagazine.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2503,125711,00.html

Link is from HydronicPros.com

Jed

hr

Multiple boiler articles

Is this what you are looking for?

http://www.pmengineer.com/CDA/ArticleInformation/coverstory/BNPCoverStoryItem/0,2730,83529,00.html

http://www.pmmag.com/CDA/ArticleInformation/features/BNP__Features__Item/0,2379,25216,00.html

hot rod

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Kal Row

for those that dont get it...

“pump-to” or “pump-away” - is not To or From the boiler, - but rather to or from the point of “ZERO PRESSURE CHANGE” - which is the point where the expansion tank connects to

The reason that point is called the point of zero pressure change, is that system dynamics like pump flow or resistance cant change the static pressure at that point, only expansion, via heating, or changing the set point on the fresh water pressure regulator, can change the pressure at that point

Now, we usually put the expansion tank past the boiler, since we connect to it, the air separator, and the fresh water inlet, and we can extract the most entrained air, at the hottest and highest static pressure point – so that’s why many people think of pump away as “from the boiler”

Now, in fact if you have a system that runs at high temps mostly (past 180) and it has non water cooled/lubricated pumps – then you want those pumps on the return to the boiler where it’s cooler for the bearings – but then, you have to put the expansion thank on the return line preceeding the pump, however, even with such a setup, you would still put the air separator (and water inlet) past the boiler at the hottest point

We put the water inlet past the boiler since we don’t want to autofeed cold water into a hot boiler

Ted_9

The exact article was in Engineered Systems Vol.21 No.6 June 2004, but Im sure these other articles will have the same information.

siggy

multiple modulating boiler article

There are a couple more reasons for pumping into the newer modulating boilers:

1. Some use an internal pressure switch that stops the burner when water pressure drops below a certain threshold. Pumping into the boiler increases boiler pressure and thus helps prevent nuisance tripping of this switch.

2. Increasing the pressure in the small low-mass heat exchangers tends to prevent of steam flash when operating at higher temperatures. The higher the water pressure, the farther it is from flashing to steam (for a given temperature). Given the tiny water content of some of the new stainless heat exchangers this is a crucial detail.

Siggy

Kal Row

That must be why

pool heaters use double ended pressure sw (cuts off both low or high) so when closed, it automatically implies a good pump, clear filter and no cracked open outlet pipes - since the have small very thin HX's and cant take a lot of thermal stress – a flash to steam would blow it on the spot

Bryan_16

Timing

I am starting a job identical to this. Will use 3 Munchies and 5 zone pumps. Anything hiding out there that I don't kn
ow about? Any heads-up would be appreciated.
Bryan