I'm going off the menu system in WB showing about 7c difference (sometimes less). All rads (even the towel rail) are balanced to around 10 to 12c difference. Internal bypass is something that I don't know anything about though John, not even sure if my WB Si Compact (2014) has one or even is it something a householder, like me, can alter?
On another note, am I actually doing right at achieving a Delta of 10 to 12 c at the rads, would I be better going for something like 5 to 8 c difference thus giving me a higher mean temperature and obviously higher rad output and then able to use lower flow temps with reasonable heat up times?
EDIT : just looked at the manual and indeed it has an internal bypass.
If you need to find a tradesperson to get your job done, please try our local search below,
or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Please select a service and enter a location to continue...
Are you a trade or supplier? You can create your listing free at DIYnot Local