FERROLI COMBI HAWK II BOILER

FEROLI HAWK II COMBI BOILER

I NEED TO CHANGE THE TEMP SENSOR IN THE CH PIPE - NOT SURE HOW. I SUPPOSE I NEED TO ISOLATE CH FLOW AND RETURN PIPES. THE BOOKLET REFERS TO FLOW AND RETURN COCKS BEHIND JIG BRACKET. I CAN LOCATE BRONZE (?) ELBOWS WHICH HAVE A SCREW HEAD ON EITHER SIDE OF ELBOW, THESE LOOK MORE LIKE GRUB SCREWS THAN VALVE OPERATORS. TURNED ONE WITH DIFFICULTY AND HAD WATER APPEARING UNTIL I RE-TIGHTENED. WILL BE GRATEFUL FOR ANY GUIDANCE, THANKS IN ADVANCE.

Please don't use capitals - hard to read!
First off drain some water from a Drain Cock not the PRV, to let the pressure off the system.
The iso valves usually have squareish heads with a slot. 1/4 turn, put the slot scross the pipe for off
The often leak, but usually stop when put back to their on position. Try pulling a bit and wiggling into place, with pliers. Often they drip for a day then stop.

Chris R

Thanks for the prompt reply, sorry about the caps, new here.
The iso valves you describe are what I was looking for, all I see are what appear to be brass (?) grub screws with very shallow screwdriver slots, already much worn from previous screwdrivers. What I don't understand is that there appear to be the same thing on the opposite side of the elbow, can't see it, only feel it.
Do you think the 'grub screws' are the iso valves? Am I just being chicken?