Store Temperature too low

Hi,

Our radiators are nice and hot but showers and hot water are just warm and go cool after a short time.
The store calling temp T1 shows 65 and T1 off shows 68. (If I press in a different order, it shows 70 and 77 though!  Not sure why!)

However, the actual readings fluctuate a bit and are around:
T1 46
T2 40
T3 H41

There are no error codes.  Could it be the boiler?
I'm also wondering if the plate heat exchanger could be scaled up as we live in a hard water area. Can you put scale inhibitor into the system, into the F&E tank?

Many thanks

The heat exchanger being scaled is a possibility and the small tank should have a treatment such as Fernox or similar to protect the system, this will not stop scale on the cold water side of course as you cannot treat that side. One thing to check is that there is enough water in the system, so correct level in the header tank. Another symptom of this is lots of gurgling. Is the hot water circulation pump set at max speed as recommended by Gledhill?