I have an L8148A with 3 zone valves and a circulator wired to it. I just added a second circulator with two more zone valves. The second circulator is being turned on by an added R8845U relay box. When either of the two new zone valves call for heat the second circulator turns on. The problem I'm having is when the furnace temp drops to its low limit I would expect the L8148A to turn the furnace on even the three zone valves on that box is not calling for heat. But the only way I can get the furnace to turn on is to turn on one of the three zone valves on the L8148A. Am I wrong in my thinking or do I need to wire the R8845U to the L8148A somehow?

I have an L8148A with 3 zone valves and a circulator wired to it. I just added a second circulator with two more zone valves. The second circulator is being turned on by an added R8845U relay box. When either of the two new zone valves call for heat the second circulator turns on. The problem I'm having is when the furnace temp drops to its low limit I would expect the L8148A to turn the furnace on even the the three zone valves on that box is not calling for heat. But the only way I can get the furnace to turn on is to turn on one of the three zone valves on the L8148A. Am I wrong in my thinking or do I need to wire the R8845U to the L8148A somehow?

Just apply logic. If you did all that work to install the second circulator figuring this out should be a snap for you. Any time a zone valve opens on a call for heat the only way the hot water can get pumped to that circuit is if the circulator serving that zone/circuit valve is running. I have 3 zones here but only one circulator. My control system is different than yours but it should work the same way. You need to be able to activate the circulator on a call for heat. Look at these wiring diagrams that show the pump hook up and see if you can make it work. NOTE: Always recheck your wiring to be sure you do not create a short circuit and MOST important keep your 24 volt control circuit out of the 110/115 volt circuits for the pump or you will fry the low voltage. Here is a link for the Honeywell diagrams. Be sure to use the correct one for your controls setup.

http://www.pexuniverse.com/docs/pdf/R8845U-Honeywell-Universal-Switching-Relays-Installation-Instruction.pdf