Hot and Cold flow rates are varying drastically

[DaveSRayner]

I have recently had a Worcester & Bosch 30 CDI (Condensing Combi Boiler) installed in my 3 bed house. Unfortunately the plumbing firm who installed it were not nice people and once they were finished we didn't want to go back to them with any queries or issues as it became apparent that they'd be met with aggressive dismissal.

Since the boiler has been installed on the ground floor we've been living with this problem - I would appreciate finding out if there is any way to fix it:

When we turn on the hot tap in either the Kitchen or Bathroom we get a good rate of flow.
When the cold tap is then turned on to full the rate of flow from the hot tap stops entirely.

Is there anything that could be done about this? Is it worthwhile calling out another plumber?

Thanks,

Dave

 

[sturharv]

When you say 'stops entirely' do you mean nothing comes out of the tap at all, or just a trickle.

One thing you will find with combi boilers is that if you have one hot tap open, particularly the bath tap, and then you try opening a second hot tap there won't be much coming out.

This is because a combi can only heat so much water at once.... 30kW will typically heat 12 litres / minute, if the first tap is drawing say 8-9 litres / minute then there is not much available for the other tap.