Vokera Compact 28 very high pressure&cutting out?

My Vokera Compact 28 reads as having pressure of 3/4 and will cut out, displaying red light if I try to have heat up beyond a minimum level. I also don't find any info on the Compact 28 anywhere online. Someone suggested the stat was to blame? The external overflow has water soming out of it, I assme this is to keep pressure down.