need help with heat balance

Jeff Hutter

Hope this makes sense: I have a 29 unit multi family. The boiler is a Weil Mclain low pressure 2-pipe steam thats top fed. I believe it was installed about 10 years ago (before my tenure) and contolled by an R&D Controller with 4 sensors. For the past 3-4 years I have been dealing with an incredible inbalance of heat from the top floor units to the 1st floor units. Temps readings are 74 to 80 degrees from the 2nd floor to the 4th floor.The first floor barely breaks 65. A month ago all the thermostatic traps (radiator)were replaced as well as the line trap (B&J FT54)...nothing changed. I took temp readings on the lines as well as the return lines. With the boiler cooking for and hour the first floor traps read 145 degrees yet the top floors roasted at 190 to 200. This tells me that there is a pressure problem 'cause I'm not getting steam, checking the boiler guage it didn't move from 0. Are there any suggestions on what my issue is? Thanks

ttekushan_3

if the return vents

in the basement aren't blowing steam, then there is an issue of inadequate steam volume from the boiler. Its not a venting issue because you have no pressure developing.

Are the radiators still cold when you take those trap temperature readings? It is possible that the traps responsible for venting and draining the mains are bad. These would be at a drip station at the and (and along the way) that connect from the main(s) to the return.

If things seem OK there, the boiler may be undersized or underfired. A pro should come out and see that the boiler is clean inside and out, and that the firing rate is correct. Once the firing rate is confirmed or corrected, you can compare the figure on the boiler rating plate that says "square feet steam" to the radiator sizes you have in the building. Steam boilers are not sized to heat loss but to the amount of radiator surface area (equivalent direct radiation, EDR). The radiators were sized first, ostensibly to the heat loss of the building. THEN the boiler is sized on that plus a suitable pick-up factor to accommodate the purging of air and the preheating of piping and initialize radiator heating. What may be happening in your case is that the steam reaches the first radiators and the condensation of steam is initiated there, creating that "pull" the condensing steam creates. If the boiler is short of output for the job, the last in line won't get anything for a long time.

-Terry

Concerned Apartment Owner

New to this but interested in the topic.

Hi All,

I live in a high rise apartment in NYC with steam heat.. uneven steam heat that is. Jeff, I noticed you mentioned taking the temperature of the lines and the returns. Are you doing this to see if the traps have failed? Though I wouldn't call this the most scientific method, I have one return line in my apartment that I can hold while there is another I can't even touch. As you can guess the room with the return line I can touch is the coldest. Terry, do you know of any sites that explains balancing a steam system? I've searched the web but have not found anything that was helpful. I'm just wondering if I should have a steam pressure gauge installed on my radiators LOL.. Hey if it will work why not. Thanks

David L. Taylor

I'm not a mechanic - just a building Supt.; but have experienced a similar problem. It turned out that the horizontal return line run (from after the radiator trap to the return line riser) was plugged. I understand that the correct way to remedy this is to replace the plugged line under the floor; but my boss did not want to break up the floor, do all that work, etc. Although it is NOT the correct way to resolve the problem, you might get away with a cheap fix by installing air vent(s) on the first floor radiator(s). We did it with 3 radiators which shared a horizontal return line on the 2nd floor of a 15 story building and it worked out fine; but no guarantees from this Supt. that it will work with yours. If it doesn't work, or causes problems, just remove the air vent(s) and plug the opening. If you do it, I'm interested in knowing how it works out. Good luck.

gerry gill

how are you venting the

down feed mains? if using just an f&t trap, they are terrible venters..are the top radiators throttled back with orifice plates?..as Terry said, check boiler sizing too..my mind is seeing this--top floor radiators heavily condensing steam..vacuum now being induced..bottom radiators with atmospheric pressure (via the return)..if i were the steam i'd go to the radiators with the greatest vacuum taking place..you may need to massively vent the mains..

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