baseboard not hot on top floor

super

Can anyone help me with this problem: I have a 8 story building 110 apts.The water leaves the boiler at 184 deg and returns at 180 but when I check the water inside the baseboard radiator on the last floor the water is 135 deg. I was told by another super to get the plumber to install a spigot at the top floor supply riser and bleed the line of air and water until it gets hot.My riser already have vents on the supply and return side.The pressure seems to be good.
Since this is a closed system I'm not supposed to bleed lot water out the system right? Is there another way to get the baseboards hot?

Al Letellier

hi-rise no heat

Ask yourself these questions. Did it ever heat correctly before? Is this a new problem? If it did work, what's changed? If it never worked, was the design correct to start with. It may be pressure related, or the circulator could be wearing out and loosing head. You're getting some water up there so it's probably not pressure related. You're delta T seem quite low for that size system. 4 degrees???? Is there a separate circulator for that floor? What is the distribution/control system and is it working correctly? Lots to consider here. Good luck.

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Jerry Boulanger_2

Balance

This could be a balance problem. Some branches in the system may be overflowing and returning water to the boiler at close to the supply temperature. Other branches are starved for flow and although they will have high temperature drop, the overall impact will not be enough to drop the temperature of the return at the boiler. A classic example of this is a hot water unit heater installed in the boiler room and piped from the discharge of the pump directly back to the boiler return. Without some type of flow control, that type of installation can overflow by many times its design value (robbing flow from the rest of the system) and return all that water to the boiler at pretty much the same temperature it left.

Mark Eatherton1

Boy does this sound familiar...

PRovided that you have adequate pressure to lift the water to the top floor without any pumps being on, it sounds like a short circuit problem. If you have two pumps, and only one runs at a time, try closing the valves off to the pump thats not running and see what happens.

A lack of check valves will KILL circulation on parallel pumps.

ME