Weird wiring/pump over run

[Bibbs118]

Hi,

I've got a rewire job next week.

The current setup, old cast iron boiler with pump over run, (currently wired so pump over run isn't working).

There is a (new) 2port and pump to the cyl with cyl stat with bypass.

There is a bronze pump for DHW

There is a (big) pump for the CH. (And what I think is a commercial zone valve currently not wired in/which bypass.

At the moment it's wired that CH only works when there is a demand for HW.

I don't think the pump over run is mega important but is there a way to wire it so CH and HW can work independently, using the CH at a valve?

I'm not sure if the CH (big) zone valve is working and can't afford to replace it(currently in situ but not wired in).

To recap, what plan is a 2 pump system with a 2 port for HW called?

 

[SJB060685]

I'm not sure if that design would even have a plan name. I thought and I hope someone can correct me if wrong but if theres two or more pumps as in this case a relay would be required to prevent one pump coming on when not required? The other option is to completely redo and convert to S or Y plan, obviously pipework will need to be altered etc.

 

[snowhead]

There is a (new) 2port and pump to the cyl with cyl stat with bypass.

There is a bronze pump for DHW

Is the cylinder unvented?

Is the pump to the cylinder the Bronze pump or are there 3 pumps in total?

Bronze in DHW are normally secondary circulation pumps, either running permanently or timed separate from the Primary DHW and Heating controls.

 

[SJB060685]

I think he said bronze Snowhead, so like you I'm assuming that's for secondary return. With what he said I'm picturing programmer set to gravity and HW brings on HW pump and boiler and CH at programmer just runs to room stat and pump

 

[Bibbs118]

3 pumps in total,

I think I'll have to have both the pumps running with the DHW zone valve holding the heat from the cyl. (There is a bypass)

Or one pump on the pump over run and the other one stopping when the demand ends.