Double impeller pump cutting in/out

Wearb

My brother had a double impeller pump for pressurising the domestic water. It is only a few months old. Installer cant come back until next week and said to just turn it off.

Here is what's happening; After using any water in the bathroom the pump cycles rapidly for about an hour and then returns to normal standby mode. Probably not a leak because it stops after about an hour. Any idea what it might be?

I will have more details after I have a quick look later.

slavetothegrind

expansion vessel burst/no air?

sullzz

Ive had this before with grundfos positive head pumps , ive needed to fit an NRV on both outlets .
Although if its a negative head , id also check the pressure vessel .

Wearb

Thanks for replies. Had a look and it must have just been a coincidence with the bathroom water. It was the circulating pump making noise when the system got up to temperature. I changed it from auto to 1. Hopefully that will sort it.