Replacing all steam convectors with a steam coil.

Dennis

I have a HVAC installation in a high rise condo unit, total heat loss for the 1300 sq ft space is 26,000 btu. The builder has removed all the enclosed cabinet type steam fin baseboard convectors and capped the supply and return lines below the floor level.
The original plan was to install a Inverter type heat pump, but the owners want to explore using a steam coil in the duct system as the heat is included in their condo fee whether they use it or not.
I'm planning on installing a 2 ton cooling system, and need some advice on piping the steam coil. The blower will close to the main building steam riser and return piping suppling the condo's convectors. My only hesitation would be the large volume of condensate from the coil possibly backing up into the steam coil figuring 800 cfm of air flow as opposed to the condensate released by the original convectors. Is there a method to size the supply and return piping to the coil. I'll assume an air vent might be needed. The convectors were drained via 1/2 Hoffman steam traps. I was thinking if another condo had a bad trap the steam might cause issues with the coil.

I want to offer the customer what they want and allow them to chose the coil or a heat pump. The unit is between floors and without any convectors connected stays around 65 degrees. The heat loss did not take into account the heat the other units or steam mains. The actual heat loss might be a lot less.

EBEBRATT-Ed

I don't see an issue with what you are doing sounds pretty common.

I would put a strap on aqua stat or some type of control on the steam condensate outlet to prevent the fan from running and blowing cold air if the steam is not on.

If the steam is two pipe you need a steam trap on the coil output (condensate) and probably a control valve on the coil inlet. The thermostat would open the control valve and power the blower fan when the condensate line is hot.

26,000 btu/hour is 26 lb of steam/hour so size the steam valve to that and the trap should be able to handle 26 lbs x 1.5 safety factor (probably the smallest trap available). Use all black pipe and pitch the lines. You may need to drip and trap the supply pipe at the control valve inlet depending how far you need to run from the main.

jumper

How about one pipe? Unit heaters are sold as two pipe but I've seen them used with one pipe.