Thermostat wiring

[BertH]

I am replacing an aprilaire 8444 with a Honeywell RTH20B.  The Aprilaire had a small blue jumper wire from A to Ab. The Red wire went into red and the jumper was also in red and jumped to Rb.


The Honeywell has slots for A and Ab but the slots will only take one wire.  Do I need to add a jumper to Ab?  If so, how do I do it?  Can I use a two wire pig tail from the red into the Ab?  Please advise. 

[BertH]

I meant R and Rc

[Admin]

You just connect one wire to the R terminal and slide the jumper up as shown in the attached diagram.