Walked into my Brother in-laws house and it was 39 degrees on the first floor and 42 on the top floor.He has a Weil-Mclean gas Furnace Boiler Baseboard Pipeing that is 6 years old.Checked all the Batteries in the Thermostats and they were good.Both red and green lights were working on top of the water purity Box.Pushed up on incoming water supply Fill Valve Four times slowly and noticed Temperature gauge coming down from 180.As soon as it hit 160 the system came on.When I left the house two hours later the Temp went up 10 degrees.Could there have been a Blockage somewhere or not enough water in the system to operate.By the way that Fill Valve was replaced 5 months ago.

What you posted does not make sense to me but that is the way it goes. Normally if it had a low water condition the boiler cut off would be in play but you said the water was at 180 degrees so I guess the hi limit had it off then you added water which cooled the boiler down which allowed it to start working.

If this home is not occupied for whatever reason I would call for service to get that water fill situation fixed. In real cold weather there could be some major problems in the home without heat.

Thank you hvac 1000 for getting back to me.Plumber came to house yesterday Dec 10 and we found a leak in the system causeing the low water.

Smart move. That leak could have caused some damage if left unrepaired.