I have an old arco boiler and radiator system for heating my house. The problem I have is the thermostat itself. It sometimes wont come on unless i take the cover off and move the contacts. I went to lowes to find a replacent thermostat. After explaining to the gentleman what i had he recomemded me to a heat only dial thermostat from honeywell. I explained to him that the old thermostat had three wires hooked up to it label (R), (W), (B). He told me the new thermostat had R<W<Y hookups and that I would not hook up the wire labed (B). I went home and hooked up the new thermostat according to his instructions. The boiler system now wont fire on. The pilot light is, and remains lit. Does the (B) wire need to be hooked up somehow? Pics are of old thermostat.