Taco zone valves with Burnham boiler short cycles

bill_71

i know the honeywell powerrobbing t-stats( the millivolt ones) don't work very well with resistive motors and time delays, you have to either isolate that valve with a relay, which it sounds like you did, or add a bleed resistor to keep the power going to the stat

Phil_15

Taco zone valves with Burnham boiler short cycles

When I wire a 3 zone system using the standard Taco (hot wax) zone valves according to the Taco wiring diagram the boiler short cycles. I am using a 40va 115 vac to 24 vac step down transformer. When I use isolation relays, that is with each of the stats wired to energize its own dedicated relay coil and with the contacts of each relay applying 24vac to the Burnham controls everything works fine and the boiler does not short cycle.

Has anyone else had this problem or is it just me?

TK03

Short Cycling

What type of thermostats are you using? Sounds like the heat anticipator or cycle rate may not be adjusted properly.

A.J._2

Anticapator setting

I could be wrong but if memory serves me you had to adjust the anticapator setting to .9 when installing those types of zone valves.

Joe Mattiello_2

Anticipator adjustment

The short cycling was probably caused by the anticipator setting on the thermostat. The anticipator is set for the amperage draw of the thermostat. Taco 570 series zonevalve have a .9 amp draw, so the thermostat anticipator setting should be set to .9 or higher to avoid short cycling of the boiler. Using the isolation relays also works, because you have isolated the thermostats from the valves, but a simple anticipator adjustment would have been fine.

Joe Mattiello
Technical Support Technician
Tel. 401-942-8000 X 484
Fax. 401-942-2360
1160 Cranston St
Cranston, RI 02920
joemat@taco-hvac.com