Taco 570 bypass levers not working

DJD775

I have 4 Taco 570 zone valves that work fine during normal operation but only 3 of 4 bypass levers will trigger the burner. Should I consider replacing the heads on the 3 zone valves?

lchmb

I see many that will not activate the end switch unless the unit is powered. I wouldnt replace them if they are working in normal operation....

Joe Mattiello

570 series valve has been around for sooo many years, and still has many terrific minds wondering. Taco's staple product generates two of the most common questions related to the by-pass lever, and the unique 3 terminal connections.

The by-pass lever is intended to manually open the valve for purging purposes, and to allow water to thermally siphon through the system in the event of a power loss. If you lose power in the middle of winter, and you're able to fire the boiler, manually opening the valve to allow hot water the travel throughout your home is really cool.

However, when you pull the lever, there is no guaranty you will trip the internal paddle switch to close the end-switch. Actually, the instruction sheet will have you disconnect the thermostat so if the lever is down, and power is restored, it could damage the valve.

Another common question is related to the3 terminal connections. There are two circuits that share a common terminal number 2. 1, and 2 is the valves operating circuit using a thermostat and 24 volt transformer to power the valve when normally open thermostat switch closes.

The other circuit, an auxiliary control switching circuit connected between terminals 2, and 3 is a normally open switch is usually connected to a boiler control equipped with it's own power supply. This generates many calls, and for obvious reasons. Most believe the two power sources will collide causing smoke to exit one of the two transformers.

However, while two circuits touch at terminal #2 they do not communicate or interfere with each other in any way. Each transformer shares one terminal # 2.

DJD775

Thanks for the wealth of information.

Bob Bona_4

The green heads never tripped the end switch, but I've been able to make it happen with the gold heads. Joe, were they the 555's?

billtwocase

Some Golds won't pull in "T-T" either. If you have to leave it in the manual position, and don't want the boiler firing, simply disconnect the #3 wire on the head