Many of us live in single-family residences lacking emergency power. While most major blackouts have occurred in summer or fall, a few (such as in January 1998 in Quebec and December 2002 in the mid-Atlantic states) resulted from ice storms that literally pulled down power lines. When such outages last for several days, they create the potential for freeze conditions when heating systems (nearly all of which need power) stop running. Small gasoline generators can provide backup power, but are expensive to install, require storage of gasoline (a potential fire hazard), and create noise and fumes. Is there a better and cheaper to provide backup power just to your heating system?

An Electrical Epiphany

In the spring of 2002, we moved into our present home (a 1962 ranch in a wooded area) and found that the reliability of the local power delivery system was a bit below par. Frequent brief outages were a nuisance for running a computer or anything with a built-in clock lacking digital memory. The August 2003 Northeast blackout raised the question of how we would deal with a loss of our central heating during winter.

A neighbor had installed a system involving a gasoline-driven generator, automatic transfer switch, fuel storage tank, etc., for about $4,000, but that seemed like overkill. All we really needed was power for the oil-fired hot water heating system.

While adding several small UPS systems (essentially batteries accompanied by inverters to convert D/C to A/C power) to support computers and their auxiliaries, I found power storage options for feeding small plug loads (e.g., lights, radio, TV, small appliances) had improved in recent years. Those with power sufficient to fire an oil burner with a 12A startup load were, however, either too expensive or required special wiring. Once running, my heating system (new in 2002) pulls only about 120 watts. Since oil-fired hot water heating systems cycle intermittently (except on coldest days), a few hours of run time are typically spread across several days. Bottom line: a power source was needed that could handle a large startup load, but only needed to store a small amount of energy.

Enter Xantrex

Xantrex Technology Inc. (www.xantrex.com), is one of several makers of rechargeable backup battery systems for residential, small commercial, and mobile loads. Ideal for my needs was the xPower Powerpack 1500 (find it at: www.xantrex.com/web/id/63/p/1/pt/5/-product.asp). Essentially a 60-pound sealed lead acid battery on wheels, it has a built-in inverter, charge indicator, standard outlets, charger, etc., plus a removable handle for easy maneuvering. Holding about .5 kWh, it can start loads up to about 25A. Xantrex also makes smaller units (one backs up my 9-in. desktop color TV) and larger (non-portable) systems that can serve appliances or larger loads (e.g., furnaces with fans).

When it came time to upgrade the house's electrical system (which had a 40-year-old fuse box), I ganged all loads related to the heating system (burner, circulator, thermostats) onto one circuit. We wired in a triple-throw 30A disconnect (which was the smallest I could find to handle 12A) with a plug that allowed me to switch the boiler from utility power to battery power, separately from other loads (see photo).

Total cost for this system (installed by a licensed electrician) was about $800, of which the Xantrex unit was less than $350. Those desiring longer operating time, or having heating systems that draw more power, should consider a larger Xantrex (or similar) unit. While no multihour blackouts have yet truly tested the system, it worked perfectly during several hour-long tests.

A Most Important Lesson

When integrating inverter-based power into a home system, remember this important lesson: inverters cannot be wired like generators. When wiring up the switchover system, not only must the wire carrying utility power be broken by a switch, but so must the neutral and the ground, all at the same time. Otherwise, the inverter sees utility power feeding back into it, causing it to blow up. (Don't ask how I discovered that fact.) ES