Yes it will run all the time. To wire it up using a Philips screwdriver open the box on the side and you will see 3 wires. Black white green. I hooked mine to a timer so it only runs when I need it to.
Try calling them.
An R8145G is a cad cell burner relay and an R845A is a circulator relay. Thus they are for completely different purposes. If you would like to talk about your system you can give me a call at 978 651 3301 Chris
Without seeing your installation, usually a mixing valve has pressure on the feed side and will feed into the loop as the pump pulls or pushes the water
I am not a pro. But it would run constantly if the thermostat is asking for it. Is the temperature not going up in that particular zone? You may want to check and release air in the system. If the Pump gets too hot; its going to fail and you will have to replace it. If I were you I would look to see why its running all the time. Check to see the temperature and pressure of the furnace.
Yes at Home Depot
Sounds like you have air in your zone
Pumps can be rebuilt using the repair kits, it may be easier and cost effective to just replace
The best way to answer the question is YES! All you need to do is buy a replacement with the same flange size and you are good. If you can't then you need to replace the pump and flanges and then still good
If your pipes are secure, it should not be an issue. The pump is fairly light.