It has come to our attention from technicians in the field that they have been having issues using Honeywell T87 Mercury Free thermostats with Carlin Primary controls. Through testing in our lab, we have found the Honeywell T87 Mercury Free thermostats are not backward compatible with all primary controls already existing in the field. This condition only exists on a warm air or a steam system when the thermostat wires are connected directly to the primary control.
The Honeywell T87 Mercury Free thermostat uses a battery in its operation process, and requires power from the primary control to maintain the battery life. If the thermostat is not wired as follows, it may operate normally for a short period of time and then stop functioning.
Please note the following wiring procedure when using Honeywell T87 Mercury Free thermostats and Carlin primary controls.
48245 – Polarity is not an issue and the T87 Mercury Free thermostat will work fine
40200 / 42230 – Is not compatible and the T87 Mercury Free thermostat should not be used with this control
50200 / 60200 / 60200FR – Note: On these controls the label does not differentiate between T1 & T2. The T terminal on the left is T1 and the T terminal on the right adjacent to the F terminal is T2.
“R” must be wired to T1
“W” must be wired to T2
For any questions, please refer to our Technical Support Hotline at 800-989-2275.