hi My thermostat has been replaced 4 times and zone valve serviced, but heat in my ap tiartment goes on and off at random. It's an old concrete building with reverse thermostat system. Heating guys are baffled. I only have one zone valve in my apartment and it seems to be new and working. So far thermostat has been replaced 3 times and nothing seems to help. Any ideas? Suite did have a burst pipe about 4 months ago before I bought the place that was fixed by restoration company. Could they have srewed something up? Problems started after burst pipe was fixed. (I think). Thanks

Brand and model number of the thermostat being used now.
Brand and model of the zone valve being used now.
Without complete information it is near impossible to provide any assistance.

Note part numbers/brand/model numbers and names will all be on your bills from the HVAC companys.