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
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Bill McCaslin:-
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Mild payback for the nasty ones |
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Don't put up with it |
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Don't let Spyware ruin your day |
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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
