Adding a steam to water hx on to a one pipe system

Dave_42

On a recent project an owner wanted to add an addition onto their building. In the new spaces they wanted to have both heat and AC so we added small fan coils with hot water and DX coils. The existing building was heat only and served with a one pipe steam system. About 3yrs earlier the owner had repalced the existing boiler and at that time the boiler was to be sized for a future addition. Has anyone ever added something like this on to a one pipe system?

In order to get our hw water for our fan coils we added a steam to water HX to the system. We now have an issue of not getting any heat to our new system. the addition of the heat exchanger has also cause some problems with the existing building. They have since gone back and added TRV's to all the radiators which have solved some of the issues. Another question is that the TRV's do not have vacuum breakers and the existing one pipe system does not have any end of line vents. Should we add end of line vents? Should they have had TRV's with vacuum breakers?

Al Letellier

system yoes

It sounds like a sizing problem, bu tyou didn't say what problems were happening. TRV are generally used to cure overheating in a steam system. Yes, there should be vents on the ends of the mains. Did you use TRV vents on the rads? You should have vents that break the vacuum to make things work proper. E-mail me with details of the problems you're experiencing and I'll be glad to try and help.

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