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# Does EDR lead to oversizing?

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Member Posts: 11
Hi I believe in Dan's Lost ART of Steam it would say to follow the E=D=R method since it is the system you have to satisfy and create steam pressure differential, as oppose to hot water systems where you should have the heat loss done and satisfy that and make sure you have enough E=D=R to distributed that energy at said water temperature!

But Dan could correct that or you could open his book!

FERN

• Member Posts: 140
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I am replacing a steam system that is not operating. I sized the house using EDR for the radiators and convectors (ballparked these).

I was chatting with an engineer friend of mine who said in his experience EDR is the most heat the system can produce and that the most accurate way is to analyze the fuel used over the heating degree days. In my case, this isn't an option because I don't know the fuel usage.

This person claimed that if sized using this method the size will be ideal and that the radiators will all fill with steam, but the steam will condense slower than if sized using EDR.

Any thoughts?
• Member Posts: 3,078
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gwgillplumbingandheating.com
Serving Cleveland's eastern suburbs from Cleveland Heights down to Cuyahoga Falls.

• Member Posts: 33
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steam systems must be sized with the EDR method. you must be able to create enough steam to fill all the radiators, or some may not heat.

hot water systems may be sized based on load calcs, fuel usage, and other methods.
• Member Posts: 6,928
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Steam boilers must be sized based on the ability of the system (radiators, convectors, piping, etc.) to condense steam. Use too small of a boiler and even though it may well produce enough energy to heat the house, the system will not fill with steam fully or evenly and both comfort and efficiency will suffer.

Your engineer friend is correct that careful analysis of fuel use can be used as a sizing aid--for hot water systems. A heat loss calculation should be made as well however as it's extremely difficult to estimate/measure the actual system efficiency.
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