ANSWER FOR HOT WATER BOILER HEATING

The term that your consultant / contractor is referring to is the method that he used to establish and select the equipment heating outputs and for pipe sizing. In your particular case he is basing his selection on a 20 deg. temperature drop between supply water and return water temperatures. Generally the established norm is 200 deg F supply water (EWT) and 180 deg. F return water (LWT). This is very common rule in the heating profession.

However, if you were interested in installing a more cost effective system, we would suggest that the system be sized based on a 40 deg. delta T. This would mean that the heating equipment would be selected for say 200 def. F (EWT) and 160 deg. F (LWT). Your consultant / contractor may question this approach at first, since their heating equipment price will go up, but the true area of savings will be in the supply and installation of the piping distribution system. As an example a 5,000,000 BTU boiler system sized on 20 deg. delta T will require 500 gal per min. flow, which requires 6" piping. Whereas, the same 5,000,000 BTU system on a 40 deg. delta T will require 250 gal per min. flow, which requires 4" piping. The piping size reduction affects the entire heating distribution, so the piping savings can be significant. Also from an operational cost, you will realize significant power savings on the 40 deg. delta T approach since heating pumps will be smaller in size. And, from a system response factor you will find that the 40 deg. delta T system will act and respond far far quicker simply because of the reduced mass of the water in the system.

If you find that you consultant/contractor is reluctant to discuss this with you, keep us in mind, our office actively designs hot water systems. Simply contact our office.

  AGROPONIC INDUSTRIES LTD.
908 RANCHVIEW CRES. NW., CALGARY, ALBERTA, CANADA, T3G1P9
ph (403)241-8234, fax (403)241-8234
Email: agropon@agroponic.com, ULR: agroponic.com

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