46 JANUARY 2017 | FUEL OIL NEWS | www.fueloilnews.com
or in simple language:
transformer VA = required VA x
applied voltage (24 VAC)
Okay, so how about a working exam-
ple. Let's say that you have five Honeywell
V8043A zone valves, Figure 8). Each of
these zone valves requires .32 amps of
power. So your required power is .32 amps.
.32 amps times 5 equals 1.6 amps. Now
you multiply that by the voltage, 24 volts.
1.6 times 24, which equals 38.4 VA.
Looks like you need a 40 VA transformer
and let's try another one.
This time it's 5 of the older Taco 'heat
motor' zone valves at .9 amps each, Figure 9).
.9 amps times 5 equals 4.5 amps; 4.5
amps times 24 volts equals 108 VA. In
this case you need a 100 VA transformer.
Are things starting to fall into place? Some
manufacturers have their own way of com-
puting necessary VA, but I've always gone
with this formula and had zone valves last
up to 40 years and that five zone example
was in my last home. One powerhead in 40
years isn't bad. By the way, as far as what
last longer, try one powerhead against
three circulators on the same job in 40
years. I love zone valves!
See ya.
l F O N
George Lanthier is the owner of Firedragon
Academy, a 25-year-old Massachusetts
Certified School teaching both gas and oil
and other heating subjects. Firedragon
Academy has its hands-on training facil-
ity in Sturbridge, Massachusetts at the
Beckett Training Center. Firedragon is
also a publishing firm publishing George's
over 60 books and manuals on HVAC
subjects. He is a CETP, NATE, NORA,
PMAA and PMEF Proctor and has been
a Massachusetts Certified Instructor since
1975. He can be reached at 608 Moose Hill
Road, Leicester, MA 01524. His phone is
508-421-3490 and his website can be found
at FiredragonEnt.com
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
