The Elderly,
The Infirm and The UPS (Uninteruptable Power Supply)
A few days ago we had a power outage in our town. Ordinarily a power
outage lasts no more than a few minutes, however this one lasted for
many hours. Therein lies the rub. For most homeowners a generator to
run the house for even a few hours would be a luxury. For those with an
invalid or a semi-invalid parent they may not think it is an option.
However, there is an option. A generator powered by diesel
or perhaps by natural gas with an automatic start and automatic
switchover is going to be quite expensive. Figure a minimum of
$6,000.00. However a little calm thoughtful pre-planning will reveal a
solution which provides nearly the same utility and can be had for 10%
to 20% of the cost. I'm talking about a UPS. In my case I have a
semi-invalid parent who is sometimes at home alone. If the power goes
off and she's reclined in her lift-chair -- well she's stuck. At night
if the power goes off there's no telling what she can run into in her
wheelchair.
The solution was to run three
separate circuits. One with a "steady on" to her lift chair, television
set, walkabout telephone, and a fluorescent floor lamp. The other two
circuits switch on when the power fails, this is accomplished with 3
pole double throw relays. One 115 Volt circuit snakes through the house
and is connected to a small fluorescent light flush mounted in a
ceiling fixture in each room. The other has a companion time delay
relay on the HVAC (heating ventilation & air conditioning)
which provides power to the blower so that natural gas or oil heating
will continue. The time delay is set to 30 minutes. This accomplishes
two goals:-
1. Iit eliminates starting HVAC if the outage is 30 minutes
or less, more importantly
2. I t reduces the Starting Power
requirement and the cost.
To calculate the size of the required UPS add up the power requirements
in watts. A fluorescent lamp of 200 equivalent "watts" literally gives
the same light output in lumens as a standard 200 Watt incandescent
lamp. Please note it probably uses 45 Watts of power. Read the package
or the label on the ballast unit itself. Do not confuse the misuse of
"watts" to describe light output. To further confuse things the power
requirement of most devices is listed according to W=VA or Direct
Current Watts = Volts * Amps. This is the formula for DC (direct
current) power. It provides a built in safety factor for electricians
and homeowners because AC (alternating current) is more efficient. FYI:
60 Cycle Alternating Current Watts = Volts * Amps * Sin 45 Degrees. The
Sin of 45 Degrees is .707. It is recommended you use the DC formula to
calculate the power requirements of each device.
If you plan to design a
system of circuits which will not be changed and to be supported by a
UPS use the Starting Watt value printed on motors. Most motors have a
relatively high Starting Watt value followed by a significantly lower
Running Watt value. Use the recommended Watt value for all other
devices. Therefore apply this formula to the sum of the Starting Watt
values added to the sum of the Wattage of all other devices -- Watts =
Volts * Amps. Now, when done, your
grandmother who lives alone in Far Away will be comfortable and safe.
The scenario is as follows.
Sleet and freezing rain coat the power lines in the neighborhood. The
feeder lines from the substation are directly exposed to the wind.
Additionally warm water from a local industrial plant's wastewater
discharge pumps clouds of vapor into the air. The wind is blowing in
exactly the wrong way. The streets have glazed over. At 07:13 hours the
line gives way and the loads are lost. When this happens the substation detects infinite
load and the substation computer takes the station off line. At 07:17
lines begin to fall all over the place.
1. When the power outage
occurs her lift chair, walkabout telephone, television and floor lamp
won't even blink. Most likely she will feel no anxiety as she won't
even know the power has gone out.
2. A fluorescent lamp will
come on in important room. These lamps will draw very little power. 5
rooms = (about) 110 Watts.
3. Should the power not come back in 30 minutes the HVAC system and
or furnace will come on providing heat. This only applies to furnaces
using natural gas or fuel oil. No provision is made in this plan for an
electrical furnace or a compressor.
In the States it is
recommended you purchase a UPS unit able to draw current from a 230
Volt circuit, and alternately from the 115 Volt leg. Stateside, power
metering is done on the 230 Volt circuit. YOUR POWER COMPANY
WON'T TELL YOU ABOUT THIS If you have an excessive 115 Volt load on one leg you effectively get
half the power you are billed for. Check out "Load Balancing" you may
be in for a surprise. If it is an old house which has been remodelled
it probably would be a good idea to have a licensed Electrician check
and balance your load. Doing so could significantly reduce the
electrical bill and pay for itself in less than a year. In the UK,
Europe, and other places where your single leg circuits are not 115
Volts but instead are 230 Volts a similar approach would be recommended
as the metering method is the same. Now don't call up your local
computer store or electrical supply house and ask for a 5KW UPS. They
will peel the checkbook right off you! Instead go to one of the auction
sites on the Internet such as EBay and watch the bidding and final
prices on some larger UPS units. Check the manufacturer's site for
several units to see about getting specifications, repair manuals,
parts and inquire about the cost of replacement batteries. Take your time learn the
market and make the right decision. That's what I did. I bought a
5KW UPS including shipping for $735.00. I charged the batteries to 100%
and tested them individually, then I ran the UPS down to 75% capacity,
repeated the tests, doing the same at 50% 25% and at fail out.. The
test load was as close as I could come to the real thing using a 230
Volt blower motor (to simulate HVAC), a TV, incandescent lights and
fluorescent lights. I
plugged the numbers into a spreadsheet and graphed each battery. It was
immediately obvious which ones needed to be replaced. This was done at
the cost plus shipping of $244.00 . As a result, I have a 5 KW UPS in
prime condition for $979.00 with a total cost of the unit of $0.19.58
cents per watt! The circuits described would apply to either a
generator or UPS installation so their costs equal out. Please understand. This lash
up is intended to do only the things listed above. Do not connect your
deep freeze, refrigerator, microwave, vacuum cleaner, hair dryer,
curling iron, electric heater or in fact any other large or small
appliance. Again, this will keep her house warm and bright, will keep
the TV, the phones and the lift chair working for quite a long while if
need be. The process is entirely automatic. You won't have to slosh
Jerry Cans of diesel around at odd hours of the night in the cold wet
darkness. Think about it. Best of luck with your
project.-- Bill McCaslin,
~~~|H-n-T|~~~
UPS. Dear Sir Thank-you for the advice
on you web pages regards building a UPS for home use
they are very informative. Can I please ask you a question?
Can I run fluorescent lights on a
UPS. I have heard from a number of people that this is not
recommended.
Thanking you in advance -- Mr David Hart UK
Manchester
Answer:
UPS (Uninterruptable Power Supply) Circuits and a Pure Fluorescent Load
The
question has been asked by one of your readers whether a UPS can
support
a pure fluorescent lamp load. The answer is yes and no. It depends on
the
circuitry of your UPS. As most of them are rather inexpensive and every
corner has been cut, then on smaller units it is safe to assume the
"ballast" load has been removed. On larger units a 15 to 75 Watt Hour
ballast is often considered insignificant. In either case plug two 7.5
watt
incandescent night lights into the circuit. This is usually enough to
give
the UPS the impression it is supporting a traditional resistive load of
motors, incandescent lights and power transformers. This is not the
traditional solution but it will approximate that preferred solution
sufficiently that you may consider 15 watts of incandescent load for
every
1000 Watts of fluorescent load... But don't try to run an entire
building on
this formula. I'd say 5 kW is the maximum practical with this scheme.
The
problem: How fluorescent loads initiate when power is applied.
There is
no point in going into all the gory details but a pure fluorescent
load,
that being several different kinds of fluorescent fixtures or all being
of
the same kind, send noise and Back EMF. These signals sent from the
ballasts, starters and the lamps as they initiate can confuse the UPS
circuits giving the impression that there is an infinite load. This
can
result in either a breaker flipping the load out of circuit or blowing
a
fuse accomplishing the same result. The latter is the most likely. On
certain very inexpensive UPS units, the circuitry of the UPS will
simply
give up the ghost. The resistive loads will take the power from the UPS
and
also take the power from the noise and Back EMF from the fluorescent
lamps
thus stabilizing the load on the UPS.
Happy Thoughts,
Bill McCaslin DocumentImage
More interesting articles by by Bill McCaslin:-
|
Setting up a home workshop |
|
Mild payback for the nasty ones |
|
Don't put up with it |
|
Don't let Spyware ruin your day |
|
How to really use the magic metal |
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He, who will not reason, is a bigot; he, who cannot, is a fool; and he, who dares not, is a slave.
~~ William Drummond, Laird of Hawthornden
