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, Dir. Technical Support Document Imaging
Solutions, LLC
~~~|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
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