Reversing flow direction

Don Walsh

I have been asked to replace two old fuel guzzler boilers with some new high efficiency condensing boilers. The system is currently piped with two primary supply runs manifolded into one loop, and 8 zone valve controlled return lines to a common manifold. Zone valves are pretty much shot, and I have thought about trying to convert this system to Primary/Secondary piping and using pumps in place of the zone valves. In order to do "pumping away" I would need to reverse the system flow. Am I asking for problems in trying this? What am I not taking into consideration?

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Weezbo

may i ask You a ?

As you look at the field part of the system,do you have any "short" zones on the zoned manifold? Along time ago i steered off pumps in favor of zone valves ,i will share this one with you....having just looked at the elephant and seen the new boiler header sans very poorly wired zone valves and visualizing the pumps i was off and running to make the job "Look Right".well,i made a boo boo....one zone was like 8' of base board,and another had all of like 12' on it:( what a waste of my work and time no way in Gods green earth were they needed to be "Forced" circulation. So,knowing the exhuberance i had for the old idea i had of "pump the heck outa it" (i seriously revised that thought since then) that maybe you could see the idea i am trying to convey ,i thought of the question.you are well aquainted with circs so maybe i shouldnt have said anything...i am way over tired and probably shouldnt have even answered this post. thing is i was looking for the pictures and disscussion on the burnham direct vent LE oil fired boiler we had a couplea few days ago......

hr

How much load are you talking?

Do you really need 8 zone pumps and 2 primary loop pumps?

If you are convinced circs are your final decesion, why can't you use them and keep the flow in the current direction?

Sometimes installers design systems with a particular flow direction. It may be wise to have the hottest water going to the coldest areas first. Pretty common with bb as they lose heat in every emitter they pass through.

Same with radiant, I always supply to the outer loops first, or the highest loss areas.

Siggy has a great bb simulator on his HDS to plan for this drop and size the radiation accordingly, by the way.

I'm not sure I would reverse the flow direction without knowing the original design intent.

hot rod

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Boilerpro_3

This is what I do

I put two pumps on the supply piped with Check valves for automatic back up, install zone valves on the returns(with balance valves) and install a bypass line or bypass with differential pressure regulator. Each pump is sized for half the flow. When using outdoor reset, most zones will be open all the time, so by going to larger pumps you should gain motor efficiency over several small pumps, reducing operating costs.

Boilerpro