Iím no heating guy but the top photo looks to be the control for your boiler and the bottom photo is the relay outputs for your two pumps each being controlled by a separate thermostat. I see two pairs of thermostat wires coming in and two power leads going out to the pumps red and brown and a common. Power coming in on the orange and yellow it looks like with a neutral.
I donít see anything plugged into the third relay for zone 3. Do you have 2 or 3 zones and how many thermostats?
Looking at it a bit more I see a curly wire coming into the top box thatís a thermostat wire also. Could maybe the basic hi / low control box be able to control just one zone and then you add a lower box depending on how many zones you need in addition.
Just guessing here but maybe your house started out single zone and then someone wanted to break it up or extend it and the other box was added.
The upper box with the temp settings Iím sure is controlling all the zones temperature wise.
Last edited by bud16415; 01-08-2014 at 11:46 AM.