Air conditioner water Pump relay

[Propnut]

I just installed a 9000 btu Air Conditioner in the forward stateroom and ducted it to the head and guest stateroom. I’m using a March water pump to feed both units and have plenty of flow to each unit. I currently have the water pump wired so it runs continuously when the breaker is on for the salon air conditioner. Looking at pump relays and trying to figure why I need to spend $150. for a circuit board type relay box. Why can’t I do the same thing with two small general purpose $10. relays with 120 volt coils. I’d feed power to each relay coil from the pump feed terminals on each air conditioner. Power to the switch terminals on the relays would be feed from a separate circuit breaker. Everything on the boat is 120 volt. I’m I missing something???
Has anyone else done something like this??
Thanks
Don Sasser

 

[O C Diver]

No reason not to. My boat has 3 air conditioners and an electronic control box to run the water pump if any of the 3 call for water. If the box died tomorrow, I'd build a new one with 3 relays. Remember to properly fuse the circuit to run the pump.

Ted

 

[bluebyu]

My control box only turns water pump on if any one of three A/C compressors kicks on.
When temp is at set point, only the evaporator fans run.

 

[gunho1]

My March pumps overheat and shut down if I run them continuously. They run fine when controlled by the ac units.