Found everything working properly upon arrival. Customers upstairs thermostat is set for 72 but cannot get above 67. All baseboards hot both up and downstairs zone. All piping by boiler are all hot both supplies and returns. It is 0 degrees out and it will be difficult to reach set temp and maintain set temp due to fridgid temperatures. Explained to customer I could replace thermostats but they seem to be in working order, I placed thermometer near both up and downstairs thermostats and thermometer reading same temperature as thermostats. System is running normally.