Zone Valves

[lbaccar23]

Has any worked with old AC/Heating units that use Hydronic Zone Valves to contrl the Hot and or Cold water for supplying hot or cold air depending on the season? I live in a 30 yr old condo unit that has this type of set up and it seems to be working well in the summer season. Unfortunately, I moved in between winter and spring and wasnt able to tell if the heat will work when the boiler is turned on in the winter to supple the hot water to the unit. I was told that the Zone valve may be "locked/froze" Doens anyone know how to check/change/replace this piece of hardware so ill be ready for winter?

[lbaccar23]

quote:Originally posted by lbaccar23

Has any worked with old AC/Heating units that use Hydronic Zone Valves to contrl the Hot and or Cold water for supplying hot or cold air depending on the season? I live in a 30 yr old condo unit that has this type of set up and it seems to be working well in the summer season. Unfortunately, I moved in between winter and spring and wasnt able to tell if the heat will work when the boiler is turned on in the winter to supple the hot water to the unit. I was told that the Zone valve may be "locked/froze" Doens anyone know how to check/change/replace this piece of hardware so ill be ready for winter?

[LazyPup]

It may not be your zone valve, it may be the design of the system. I once worked in a motel that had both a boiler and a chiller but only had a single loop hydronic system. It was an either/or function that gave us fits in spring and fall. With 275,000 gallons of water in the system it took a lot of energy and time to switch over.
Basically for heat we would circulate 180 deg water in the loop, to change over to AC you had to valve off the steam heat exchangers, allow the system some time for the temp to fall off to 110 deg, then open the heat exchangers to the chiller and cool the water to 40 deg. The indivual room thermostates only controlled the fan motors while the coil temp was determined by what was happening in the boiler room.
Most modern systems use a two pipe system that simultaneously circulates both hot and cold water and the zone valves switch back and forth depending on the individual demand.
The single line systems have a strap on temperature sensor on the pipe. If you set the thermostat for AC it will not allow the fan to run unless the line is cool and vice versa for heat, If you set the thermostat to call for heat, it will not allow the fan to run until the line is warm.
If you happen to be in a condo with one of the old one line hydronics systems there is not much you can do. Check with the bldg engineer and he could explain your system.
A single line system works real well in summer and winter, but in spring and fall with cold nites and hot days it is an operating engineers nightmare. The actual change over from heat to AC or vice versa took about an hour and a half to complete.