Posted by Harold Kestenholz - Hydronic Network on June 20, 2001 at 09:55:34:
In Reply to: undersized boiler can cause highbill? posted by benoit g.n.c.v. on June 19, 2001 at 20:24:41:
There are a few parameters missing to make the comparison:
Were the degree-days from one year or an average of years?
Was the degree-day number the same in the following or questionable year, or the higher?
Were the boilers installed for the same customer or a new one with new usage?
Teledyne-Laars (Triangle) boilers are copper-tube (cast-iron header) low-mass boilers so their standby losses are low. Whatever small amount of heat they have to lose in the water inside the boiler and the small weight of metal are lost in a short time after shutoff up the chimney and out the jacket. This is part of the AFUE calculation which is based upon a half-time temperature of 42F. So a long shutoff time brings small losses.
In either cast-iron or copper fin baseboard systems, other complications can cause increases in consumption. Very often, new boiler changeouts include zoning. When one zone alone is open, the boiler is oversized for the radiation so the water temperature overshoots causing extra losses. Standard thermostats can set up continuous overlapping demand, where one zone calls for heat, then another, then the other, so the boiler stays at a high temperature longer than necessary. The good intention is failed due to lack of understanding of control. This would have produced even more losses if a new boiler of the same size was installed. Two-stage thermostats can prevent the problem by using heated water from one zone to transfer to another.
So it is a complex issue that needs to be examined with all the parameters. This knowledge was part of the IBR Schools seminars, so the yearly courses in 30 cities throughout the year reminded contractors and utilities of the strategies to maximize efficiency. The courses were dropped when the need to reach the country dropped back from 70 courses per year to the older 30-course yearly schedule. As the experienced join the "Dead Men," education for the energy industry relies upon magazines. (Just don't tell your children that they will have to learn the 3-R's by reading a monthly magazine - school's over.)