Anyone know how this works??

[melmos]

Went to customer house as he wants new controls. See picture for set up. There are no motorised valves, no room stats, just one frost stat outside utility room where boiler is, every radiator (37 in total) has a TRV. The boiler is a Ideal Concord CX, he has 2 programmers, 1 for downstairs heating and hot water the other for upstairs heating, all connected to the 3 pumps. When he turned the downstairs heating on the appropriate pump started and water flowed through to radiators. I can't get my head around it, has anyone come across this before.

 

[snowhead]

Instead of 1 larger pump and 2 zone valves its using 2 smaller pumps which also act as a zone control just as a zone valve would.

 

[stevetheplumber]

there should be relays to stop back feeding of current possibly in the box on the wall?

 

[melmos]

Thanks guys for your input, the set up doesn't affect my change of controls. I know from customer that everything works and has done for years, I just couldn't see how.