Model K vapor system

Steve_210

I have an old model K type vapor system, the building is 120 Ft x 50 Ft and 12 floors including the basement. We have installed orifices in approximately 250 radiators that had their valves changed from original. I have lowered the pressure to between 1/4 - 1 1/2 pounds( am waiting for vapor stat). I know originally the main vents were all in the boiler room, there are now some vents outside the boiler room on the supplys and the returns. Just wondering if the main steam supplys or the main dry returns should be vented or not? also what would the ideal pressure be for this system? I have replaced all 3 crossover traps in this system.

Any help would be appreciated.

Jamie Hall

The Model K

(ARCO Model K) used, as you have noted, orifices in the valves on the radiators.  The mains were vented through the crossover traps to the dry returns, and the whole show was vented, as you have noted, through vents in the boiler room at the end of the dry returns.  There is probably no harm to having vents elsewhere on the system, but there's no point, either, and they can be a nuisance to install and maintain.  Just put enough venting on the dry returns in the boiler room and she'll run just fine.



As to pressure, they were designed -- like all these systems -- to run on very low pressure.  Anything over 8 oz. and they start getting unhappy, so when you get that vaporstat (and a low pressure gauge; the newer vaporstats sometimes need calibration and you can only do it with a low pressure gauge) I'd set it to cut out at 8 oz. with a 6 oz. (subtractive) differential.

Steve_210

reply

thanks jamie. i already have the low pressure guage, the original valves  had adjustable orifaces (looks like a set screw inside the valve). We added orifaces to the valves which had been changed from original and drilled them out for the EDR of each rad. we also added steam traps to 2 steam coil units which had been blasting steam into the dry returns. can a system this large work on 8oz cut out. I guess i will have to wait for the vaporstat.     

Jamie Hall

Usually

the vapour system pipes were sized generously by the dead men, and so, usually, they will work on 8 oz.  It is possible, however, that you may get better results at slightly higher pressures -- but I would never let the thing go over a pound or so.

Steve_210

thanks

thanks again and a happy new year to and every body else on the wall

Steve_210

thanks

ment to type to YOU and everybody else