Diverter valves?

C/H & H/w. What a set up!!!!.

Emerging from the floor 22mm pipe which carries the pump. Continuing the 22mm on pump flow is a T off 15mm to a gate valve then changes to 22mm in to the h/w tank bottom 1/4 of side which I assume is the tank coil inlet.
Continuing further up the pump flow pipe is a 22m T off with what appears a diverter valve [has little window in it but can't see what's in it because of position] then 22mm disapears back into the floor.

Then the pump flow 22mm contunues with what again appears to be a diverter valve case has Sunvic on it no window on this one, then on to the tank two thirds up side which i assume is the tank coil return.
The hot water outlet to all taps with combined vent pipe at top of tank of course, the vent overhanging the loft cold water storage tank.
What is this system ? never seen anything like it.
We live in a bungalow so not gravity fed system.

There is also a red pump danfoss [wrong one apparently] that seems to feed a seperate hot water system, the tank side of the pipe is hot with the other side flow out cold have no idea what it feeds or fed the pump is not working no power to the cable even though its in the terminal block all wires go into from the temp: unit on tank and the two valves.
Thanks to all who bother reading this hopefully its understandable.