I am looking to replace my existing boiler (Ravenheat) with a Vaillant Ecotec Plus 430 Open Vent unit and from looking at the manual that I downloaded from Vaillant's web site, I don't believe I need to wire the pump to the boiler for pump overrun. I query this as I think that other models in the Ecotec family (system or combi) may require pump overrun. In the manual I have, there is reference to accessory relays which I believe may be setup for pump control but can anyone offer any advice as to whether pump overrun is a definite requirement for my proposed model of boiler and if so do I use an accessory relay?
I guess my second query is somewhat related to the point above and it concerns the need to have a bypass valve. On my existing setup there is no bypass but as I have a mid position valve for HW, I have been told that a separate bypass is not required as there will always be a path for the pump (if it indeed needs to overrun) to be able to dissipate the heat either though the HW cylinder or through the bathroom rad which is without a TRV. So, assuming I have to worry about overrun etc, do I need to fit a separate bypass valve?
I guess my second query is somewhat related to the point above and it concerns the need to have a bypass valve. On my existing setup there is no bypass but as I have a mid position valve for HW, I have been told that a separate bypass is not required as there will always be a path for the pump (if it indeed needs to overrun) to be able to dissipate the heat either though the HW cylinder or through the bathroom rad which is without a TRV. So, assuming I have to worry about overrun etc, do I need to fit a separate bypass valve?