Dt90e room thermostat and Halstead ace boiler issue

[TurboDog99]

Halstead ace boiler
Dt90e stat

Just relplaces my old room stat after many years of service with the above Honeywell unit.

My boiler runs off it’s mechanical timer to come on between 7-10am and 5-8pm.

The old thermostat would operate only between these times and do nothing the rest of the time, which is what I wanted.

With this new stat installed. No longer does the boiler start with the mechanical timer. The stat basically turns the boiler on when the temp setting is met and turn it off once temp is reached.

My question is, is there a way to set this like my old one? To only work between the hours the timer shows and boiler is on. Also why would it affect the boiler no longer turning on when the timer indicates it to?

The install was 2 wires like my old one. L1 to A on stat
And L3 to B on stat as stated in the halstead manual.

Any help would be awesome. Thanks.

[stoneyboy]

Hi turbodog99
Assuming you have only worked on the thermostat connections try fitting L3 onto C.
Regards S

[TurboDog99]

Thanks for the reply. Yeah I only worked on the thermostat side of things, haven’t touched the boiler.

I’ll give this a shot and report back. Many thanks!