Radiators very slow to heat up

[Anthony Gray]

Radiators very slow to warm up on ground floor.
I live in a two storey house with unvented hot water cylinder and closed CH system.
Boiler is on ground floor. The unvented hot water cylinder, water pump and expansion vessels are in the loft.
Ground floor CH has two port valve and radio controlled thermostat.
First Floor CH has two port valve with fixed thermostat.
The pump is working.
Both thermostats and two port valves are working.
The first floor radiators are working well and have been have been 'balanced'.
The ground floor radiators take 2 hours to warm up.
The CH pipe on the ground floor from the pump gets very hot but the CH return to the pump is just warm.
My suspicion is that the CH flow and return pipes are both connected to the same side of the pump - is this normal?
I have a photo of the pipes around the pump but don't know how to attach it.

 

[John.g]

Has it always been this way?, I couldn't see it working if both flow/return connected to same side.
Have you TRVs on all the ground floor rads?
Does your circ pump display the power in watts?.
what is the system (boiler) pressure?.