Worcester combi, two pumps instead of diverter valve? Hot water bleed into radiators.

[Gingerbread Man]

Worcester Bosch 350 (I believe as I can't find my notes of the model number at the mo) combi boiler. A model that has two circulating pumps. As I understand it, they replace the traditional need for a diverter valve (!?).

When they run hot water for a prolonged period, shower, bath. The radiator pipes start to come warm.

Now, I believe that there non return valves under the pumps, would one of these bleeding back through cause the problem as described.

 

[DirksPlumbing]

Re: Worcester combi, two pumps instead of diverter valve? Hot water bleed into radiat

If so you should normally find flow and return reversed for the time of the HW demand.
The 350 ist classed a G boiler. Just to let you know.

 

[diamondgas]

Re: Worcester combi, two pumps instead of diverter valve? Hot water bleed into radiat

Yes!

 

[Gingerbread Man]

Re: Worcester combi, two pumps instead of diverter valve? Hot water bleed into radiat

G rated isn't something that concerns me as it's not my boiler.

I'll look deeper into the non return valves then if that's the answer.