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Posted by walterf on March 05, 2010 at 21:06:38:
On my new cast iron hot water boiler system, 7 zones (1 hot water maker, 1 boiler water baseboard, 5 radiant floor zones with injection mixing) are supplied by 7 tees branching off a primary loop. The returns from the 7 zones feed back into the return side of the primary loop. Each zone has a pusher circulator just after the zone's branch tee off the primary loop. The primary loop has its own circulator in the primary loop. All the circulators appear to be identical, and my plumber confirmed this. I am concerned about the order of the tees and the circulator in the main loop. Starting from the boiler hot supply following around the primary loop, there are 3 zone branch tees, then the primary loop circulator, and then 4 more zone branch tees in series (downstream from the primary loop circulator), and then the return tees from the 7 zones one after another, and then you get back to the boiler return. If the 4 zones branched off the primary loop downstream from the primary circulator are all calling for heat at the same time, might their combined GPM draw exceed what the primary circulator is circulating, so they might actually start sucking return water from the zone returns that join back into the primary loop just downstream from these 4 secondary feeds? Shouldn't the primary circulator be between the zone feed tees and the zone return tees? My plumber says it doesn't really matter where the primary circulator goes in the loop because its just circulating water, which will be the same regardless of where it is in the loop. I'm just a newbie to this, so any advice would be appreciated. Thanks.