Boiler Help

smoore

I have a customer that wants a replacement boiler. He has a farm house that was built in 1900 in Iowa. It was a gravity system originally with cast iron radiation. The orginal boiler was replaced and a pump added. The home is 2700sq.ft. without basement and no insulation in walls. There has been insulation added to second floor attic with an r value of 45. The windows are original wood frame with combination storm added. Heat loss comes up to about 133,000 btu. How do gravity systems and pump systems compare? what are the pro's and con's of the two? Any sugestions on a system to give the most comfort would be appreciated.

Steamhead

Just about any new boiler

depends on forced circulation to operate properly. This is the price we pay for smaller, higher-efficiency boilers.

First thing I'd do is a complete heat-loss calculation. Go to the Free Heat Loss Calcs page of this site to order Slant/Fin's calc program, which is very easy to use. Select the size boiler needed to handle the calculated heat loss at the lowest outside temperature you get in Iowa.

Then measure all the radiation. If you don't have a radiator capacity chart, go to the Books and More page of this site and order Dan's "E.D.R." book which has almost every chart you'll need. Also order Dan's "Pumping Away" book which shows the one best way to pipe the boiler so the system does not get air-bound.

To select the proper circulator for that system, go to http://www.heatinghelp.com/newsletter.cfm?Id=125 and locate the amount of radiation you have in Equivalent Direct Radiation (EDR) or thousands of BTU per hour (MBH). The circ capacity will appear in the Gravity Conversion column. Take this figure to your circulator-performance charts and select a circ that will produce the required Gallons per Minute (GPM) at a 3-1/2-foot head. Don't be surprised if the circ that comes with the boiler isn't the right size for that old gravity job. Install the right one and the system will run more efficiently.

If you get stuck, ask us and we'll do our best to help out.

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