steam boiler replacement, condensate return

DrunkinPunkin

Does anyone know how to figure if a condensate tank and pump are needed when replacing a "huge" old steam boiler, gravity return, with new, smaller, W-M boiler? I have gotten 3 quotes from sales reps and none have addressed this issue until I mentioned it. Help please!

t. tekushan

condensate return pump

The general rule (and its definitly general) is that a new boiler over about 10 horsepower (about 350,000 btu to 400,000 btu) will benefit from a condensate resevoir w/feedwater pump. The boiler water level is better managed this way. With a large output boiler you may find that you need to start the boiler with a higher than normal water level so that it doesn't shut down on low water near the end of the cycle.

There are so many variables, though. Big one: How convoluted is the main and return piping? In the north zone of our building I actually removed the boiler feed pump and receiver assembly. We have 600,000 BTU output and no trouble with water level problems. I removed the pump because the condensate receiver was HUGE and would cool the return water in the boiler room and the pump was so large that it would put in so much cool water at once that the boiler would cease to boil for a short time. And it was plumbed into the hartford loop. So I tried using the gravity return method and its worked great.

The point is, if the system is more "vertical" than horizontal, and the return system is straightforward and properly pitched you can edge that figure of 10HP up substantially.

Without knowing the EDR of your system, piping arrangements, the length of the main(s) and the height of the building, its difficult to tell. If the new boiler is beyond 25HP (2500 square feet EDR, or 600,000 BTU I=B=R net heating capacity) I'd go for a properly sized condensate receiver and feed pump.

-Terry

RonWHC

Unless there is a GROSS difference

in water content, & the boiler is sized correctly, & near boiler piping is done "to the book", you will probably be OK w/o the feed water tank & pump. Many tank/pump combos are added to correct an installation error(s). Weil spends mucho dinero on their I&O Manual. Make sure it is followed.

Confirm the quote includes labor to flush the return lines & skim the boiler after installation. May take several days, & multiple trips, to do the job right. Ask the sales reps to check for adequate venting, & include upgrades if necessary. A tank/pump combo is another electro-mechanical accessory that requires maintenance. Try to keep it simple. Good luck.