boiler will only fire up if thermostat is manually turned up

Unknown

a mercury operated stat, or digital? That does make a diff.

george_24

I installed zone valves and new thermostats to my old boiler.The boiler is not firing up when the temp. drops to the setting on the themostat,but if I turn the thermostat
up (by hand) 2 degrees, the boiler will fire up .It won't
shut off until I manually do it.

Timco

Sounds like your zone valves are wired incorrect. What zone valves did you use? (make / model) Typically you have a LV loop that the t-stat completes sending power to the ZV. Sometimes they are voltage to open & close.

Tim

Unknown

More information please.

What kind of zone valves, what kind of thermostats, what do you have the heat anticipator setting on the thermostats set at, have you checked the thermostats temperature reading with a seperate thermometer?

The more info you can provide us the better chance at getting a more on target response.