Bypass problem h/w boiler

Mark J_2

Burnham h/w boiler (obsolete) PXG-2005 has Taco bypass Tee valve connected to main supply tapping with 3/4" bypass piping from bull of tee back to return inlet of boiler. Low supply temp. from run of tee (1 1/4") up to system. Temp. guage showing 190 to 220. Returns not coming back hot. Zones not heating. Installed throttle valve on bypass piping. When throttle valve closed supply header gets hot, system pressure stays low but zones still don't heat. Purged air numerous times from all zones.

Weezbo

ever consider the zone valves?

when you say purged air from the system i wonder what you mean by that....if the system has zone valves or an injection system perhaps one or the other is not functioning...in which case the next biggie would likely be a transformer or circulator control signal...hang any new pictures lately?

Mark J_2

Thanks for your reply "Weez". Went back to job today and believe to have found source of problem. "Taco" temperature modulating valve connected to supply tapping of high efficiency boiler with bypass has internal thermostatic element that failed. Temporarily removed element and system heated properly. Advised customer that it is safe to hang pictures on walls as long as they contain my logo.Thanks again (watch out for thin ice).

Al Corelli_2

Name of device?

Would that be a "Taco-Matic" valve?

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Weezbo

Very cool find*~/:)

was the failure due to overheat on supply side ...?

was it an I series -R ?

Joe Mattiello

Hi Guys:
I had a couple of documents on the old Taco 595 thermostatic by-pass valve stored in my electronic database. For your reference I attached a typical piping layout and the internal design so you have a clear understanding of the valve and how it’s used. Taco recently decided to obsolete this product along with the replacement thermostatic element. You can pull the faulty element, plug it, and abandon the valve.