Hi
We have a Bosch Worcester Boiler and Bosch Green water tank (pics attached). Our system is a Honeywell Comfort one we have underfloor heating in most of downstairs but also some wall radiators. Upstairs we have just radiators. Each section of the heating has its own zone and we can have the underfloor on and radiators off etc. We have been having some issues with our hot water the monitor states a "comms error" to the hot water. When this happens we have to switch the boiler off and reconnect the "comms" to each zone. We are currently waiting for our installer to come and have a look but unfortunately he has had some bereavements and we don't want to trouble him presently.
The comms issue occurred today we did the usual and asked the hot water to boost (baby's bath time!) it did click on and the water temp showed it was rising however the upstairs radiators also came on and it is like a sauna up there 
. I checked the monitor and we did not have any boost on the heating which was set to come on only if the temperature dropped to 12 (which it hadn't!).
My question is this - why?! Have we done something with the boost or did the heating kick in because the water in the tank was not hot enough and it needed the boiler to heat - but if that is the case why did only the upstairs zone come on? If you have a separate water tank surely that's what comes on to boost the water temperature not the heating? In the Summer does this mean I need to turn all the radiators off? Or does this mean a problem with the installation?
There is probably a reasonable rational explanation and I'm overlooking something very simple 
.
Thanks for reading!