We have a house with a zoned central heating system. The heating upstairs is no longer working (just as the temperatures drop again!) I know its to do with the motor housing (because there's a stamp on it saying what it is). There is a spring mechanism which moves a plastic arm and opens a valve to let the water through. For some reason it isnt opening. I've moved it manually and jammed it open with a wooden spoon to heat the house for a couple of hours. Is this dangerous though?? Could I get exploding pipses or something? 