Thermo-siphon fits

Tony_23

Read Joe's post. 24 volt ZV controlled by stat, end switch controls SR506. Real simple and commonly available.

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Darrell

Thermo-siphon fits

About four years ago I did a remodel that got out off hand...only about 110% over budget...but I digress! Retrofitted two fan-coil F/A units, an indirect water heater, some garage unit heaters, some baseboard, some radiant floors, and two cabinet wall-units with little fans. All are zoned with Taco 007-IFC's. The WMC CGS works great. My problem is that one of the Cabinet unit heaters is three floors up...about 25 feet above the boiler and once flow is established to the unit it will never quit. The Taco IFC check valve floats open enough to keep the fan blowing. I tried beefing up the spring in the IFC...still floats. I've added an in-line spring poppet check valve at the unit...still flows. I've reversed the flow through the unit from bottom to top...still flows. It's just a miserable little twin-flo unit in a bonus room...Does anybody know a trick other that adding a line volt zone valve for positive flow stop?

Brad White_2

Is there a return Flow Check?

A simple drop-loop counter siphon would be near useless against the stack effect of 25 feet of height but a second flow check might work. Amazing in that it is probably such small diameter tubing.

Are you sure the circulator is off? Have to ask. Those suckers can be quiet....

hr

Do you have check protection

on both the supply and return? You need it as the heat will ttravel up either pipe regardless of flow direction.

Hydronic spring checks or a circ with internal check on one side should work.

really shouldn't need a zv.

hot rod

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Darrell

Yeah, I built in a drop loop of about three feet on the rough-in and the tubing that I snaked through the place is 1/2 Wirsbo Pex. The circ is controlled by a Taco SR505 and it does shut off. Like you say, ya gotta ask...it's the obvious things that get missed most often in service work.

Darrell

I still have the beefed up spring in the Taco IFC which is on the supply. This is piped like an injection system with closely spaced tees off of a 1-1/4 header. I installed a second check, a spring check, in the unit at the midpoint...mostly because it was easier to put it there.

Joe Mattiello

Sounds like you dedicated enough valuable time diagnosing the thermal siphoning problem. There has to be either a pressure drop greater then the approximate .5 psi required to open the check, or high head circulator in an adjacent zone creating a pressure drop across the problematic zone keeping the check open. Installing a 24volt zonevalve will quickly remedy the problem giving you the positive shut off you need. The zonevalve will be the interface between the thermostat, and the SR506

hr

Hard to say without pics or drawings

If the closely spaced tees are pointing straight up off the primary loop you will for sure need chech protection on both supply and return. I'm not clear if you have it this way or two checks on the supply only?

Or as Joe mentioned it could be another pump in the piping pushing through that connection if it is no a true PS piping.

hot rod

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Darrell

Thanks guys for your interest...all of the zones are off the same header which is a loop through the boiler with an 007 pushing...almost no head...maybe 30 feet of pipe total and nice and clean. The tees all point down. All of the circs, (x10), are 007-IFC's, so nothing hi-head. It's summer so the house isn't calling for heat much. Last callout no other zones were calling, and judging by the cool piping hadn't called for some time. After the modifications I let the zone run for about five minutes purging the air, and then shut it down with the t-stat. The circ did shut down...I checked with an electrical tic tester and my ear bone. The siphon flow was sustained enough to keep the unit hot enough to keep the fan blowing. It's too far up there to be conduction along the water column, and there is measureable Delta T from supply to return at the unit. I'm thinking a 120v zone valve wired paralel to the circ pump seeing as how they are side by side and it wouldn't take any control magic.