Troubleshooting a zone

Eric Johnson_3

I've got 4 zones on an old Weil-McLain gas-fired boiler. I don't use the gas. Instead I have a wood-fired system that heats the water in the gas boiler through a flat-panel heat exchanger. I mention that just to provide perspective. Water temps vary from about 140 to 180.

My question is this: One of the zones (all have circulators) doesn't seem to be able to get enough hot water to the two cast iron radiators and one toe-kick exchanger that it serves, even when it's the only active zone. The other zones all work fine. There are a couple of funny things about this zone, however, and I suspect one or more of them is causing the problem.

First: it's 3/4-inch copper.
Second: water is routed to and from the toe-kick blower with a pair of mono-flow "T"s, down to 1/2-inch. The blower rarely kicks on because the water temp is usually too low.
Third: For some reason, there's a flow control valve on this zone, right where the supply line leaves the boiler.
Fourth: The circ. on this zone is an old Taco 007 that's seen better days, I suspect. But it runs quiet; no sign that the bearings are going.

All the other zones are 1" copper or larger. All have much newer circulators (Grundfos 42s or bigger). Everything is vented properly as far as I can tell, which is to say the rads and toe-kick all spit water when you open the bleeders.

I thought before I started replacing pumps, opening FC valves and re-piping the zone, some informed opinions would be a good idea.

My questions are as follows:

1.) If an old circulator runs OK, does that mean it's moving as much water as a new one would?
2.) Can monoflow "t"s disrupt the flow in the system?
3.) Why would somebody put a flow control on a zone?

Thanks!

Timco

1) You can get a variable speed pump, sounds like yours is the culprit.
2) My toekick is tied into the HW 2-pipe system like any other rad, and works great.
3) "flow control" is likely a check valve intended to not let the water "ghost" or flow backwards through a zone not calling for heat.
4) Rads radiate after getting warm. BB does not...just when circulating. The BB will never keep up with the rest of the zone unless it is large enough to warm the room while the circ was running.

Tim

Eric Johnson_3

New circ pump did the trick

I swapped in a new circulator and it works great now.

Thanks for your help, Tim.

And thanks Dan for this board.

You know I'll be back.

--Eric