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Fuse & Circuit breaker

Temperature sensing

Stand-by search mode

Inverter efficiency

Remote on - off & monitoring

A few words of advice

SAFETY

Inverter Information:

MODIFIED SINE WAVE - runs most loads except for laser printers,

some sensitive electronic equipment and some battery chargers/adapters.

TRUE SINE WAVE - runs any load (within its power output range), electric motors

will run cooler and last longer.

Some timing devices require a true sine wave to function properly.

These units are more costly than a modified sine wave model but have a

cleaner output and relieve you of the "will it run the load or not?" guessing game.

Also see: Wave Form Facts

SURGE RATING - is the amount of wattage an inverter can produce for a

short period of time to start heavy loads (motors and some electronic equipment.)

Many inverters can produce up to 100% over the continuous power rating during

load start-up.

Some electric motors draw 2 to 3 times their name plate ratings to start.

Consider surge ratings only for momentary startup, never for continuous use,

no matter what the salesperson says.

UL LISTING - when an inverter is used in a code compliant installation it must

be UL listed (UL1741.)

Some manufacturers have most, if not all, of their domestic voltage/cycle

units UL listed. Others have only a few in their line listed.

Check the name plate to be sure, in case of a fire (as with photovoltaic

modules) the UL listing can make the difference between an insurance

claim settlement and living in a pup tent.

VOLTAGE - whenever possible use the highest D.C. voltage possible.

The higher the input d.c. voltage, the lighter the cable can be.

This also allows for longer cable runs with less voltage loss.

Always use the shortest cable runs from the batteries to the inverter.

Most inverters have a higher efficiency and run cooler when set up for higher d.c. voltages.

FUSING - the fuse between the inverter and the battery is placed in the

positive cable and should be as close to the battery as possible.

Short circuits in a large battery bank can be devastating.

MAKE SURE that the fuse and block are rated for direct current (and listed)

since a d.c. fuse is designed to take a much greater amperage hit than one

designed for a.c. When you purchase the fuse or circuit breaker for your inverter,

check the surge input rating for the inverter.

If you don't, everything will be fine as long as you never draw more than the

inverter's rated continuous output.

If you ever have to start a heavy load and the inverter goes into its surge rated

output, the fuse or breaker will blow. Size the fuse or breaker for the surge

rating and you will not be dissapointed.

CABLES - the cable size (or gauge) should be the same for both the inverter

to battery connections as well as the battery to battery connections.

For the Ready Power 1500 we use 2/0 size cable (UL listed.)

Remember, the longer the cable, the larger it has to be to handle the amperage

and voltage losses.

Keep the cable lengths as short as possible to reduce power loss as well as to

reduce interference which may radiate from the cables.

Also keeping the cables close together can reduce the interference which is

broadcast by them.

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TEMPERATURE SENSING - on inverters with built in battery chargers it is a

good idea to install a remote battery temperature sensor if the batteries are

located outside or in a different room than the inverter.

This will allow the inverter to charge the batteries at the proper rate according

to the battery temperature.

These sensors are quite inexpensive and can greatly extend the life of a battery

bank.

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INTERFERENCE - AM radios pick up interference from the inverter (true sine

wave inverters produce less.)

It is best to keep telephone lines away from the inverter and a.c. lines running

from the inverter. Improper grounding techniques can also cause interference.

This is from personal experience.

It will save alot of head scratching and trouble shooting later.

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STANDBY OR SEARCH MODE- this is when the inverter is not powering

any loads but turned on. In this condition, the inverter is constantly checking

its output to see if a load has been turned on.

Once it senses a load, full power will be made available to the load.

Different inverters use different amounts of power when at rest in the

search mode.

This is an important consideration when setting up a system.

Please see REMOTE ON / OFF AND MONITORING.

Some of the larger inverters draw a lot of power once

a load is sensed, even if it is a small load.

For this reason, if you have either small loads that run all of the time

(clocks, security systems, fax machines,etc.) or small loads that run part time,

you may want to add a smaller inverter to the system just to run these loads.

It can sometimes be more economical to do this.

One reason to look at the power draw when in stand-by is the cost in

photovoltaic modules or any other alternative power source.

In the Exeltech inverter line, on the XP1100 models we only stock the

versions with the X-2 low power option.

It costs about $ 40.00 more than the standard model, but uses

10 watts per hour instead of 20 watts in stand-by mode.

That's $ 40.00 to save on at least 10 watts per hour of photovoltaic modules.

This means that if you run the inverter 24 hours a day in stand-by mode

(I am oversimplifying this) you will have to produce at least 240 watts less per

day from your solar array.

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EFFICIENCY - the percentage of power that is put out by the inverter verses

what goes in.

An inverter with a 90% efficiency rating sends out 90% of the wattage that is

put into it from the d.c. source (battery.)

The 10% difference is lost in the form of heat and vibrations.

As the amount of power increases or decreases that is pulled from the inverter

the efficiency also changes.

Some inverter manufacturers supply a graph which shows the efficiency of an

inverter at different power outputs.

Example: a 1500 watt inverter may be 90% efficient at 1500 watts but only

50% efficient at 600 watts.

In some cases, by over or under sizing an inverter you can be throwing away

energy and money.

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REMOTE ON / OFF AND MONITORING - if your inverter is going to be sitting

idle most of the time it is recommended that it be turned off.

An inverter uses from a few watts to ten watts or more of power, depending on the model, when it is turned on but not producing power.

This is called power consumption in the search or standby mode.

If the inverter is placed in an inconvenient location it is recommended that a

remote switch be installed.

For every hour that an inverter runs at idle, that is power that you must produce

(solar, wind or hydro.)

It is more cost effective to shut down the inverter when it will go long periods

in the search mode.

Having an inverter in search mode 24 hours a day, but only using it for a few

hours, wastes the output of one or more PV modules.

When considering less expensive (cheap) inverters please see what the power consumption is in standby mode.

We use an Exeltech inverter (10 watts standby mode) which powers one of

our storage buildings and provides power to exterior outlets.

To make life easier for us and to save energy, the building which houses the

system has an outdoor weathertite switch to control the inverter.

Photovoltaic modules are not cheap, why waste the power they produce or

buy modules you don't need?

Yes, I really mean that.

Some inverters, like the Trace SW and PS series offer a remote system

which allows you to turn the inverter on and off, monitor and change inverter

parameters as well as to monitor the incoming power.

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A FEW WORDS OF ADVICE. Inverters are not inexpensive.

There are many different inverters available to fit just about any need or budget. PLEASE, regardless of who you buy from, buy the best that you can afford.

Check out the specifications.

I have thrown money away by not doing this.

Many inverters can not be used full time, if you need one to run constantly,

buy the right one - not a unit that will at best, keep shutting down or at worst,

self-destruct.

Look at the input voltage range, some inverters shut down when the battery

voltage drops below 12.0 volts.

Why have a deep cycle battery bank if the inverter will not utilize it?

And what does that say about the unit's efficiency?

Look for a manufacturer that has a track record and will be around for a while

to come.

The old addage still applies "pay me now or pay me later."

copright by John Drake Services, Inc.

ALWAYS READ AND UNDERSTAND THE OPERATIONS MANUAL BEFORE INSTALLATION. PLEASE DO NOT HESITATE TO CONTACT THE MANUFACTURER WITH QUESTIONS.

SAFETY - ALWAYS treat the output power of an inverter with the same respect

as you would the power coming from the utility company.

Always follow the same safety practices and use proper overcurrent protection

devices (circuit breakers and/or fusing.)

copright by John Drake Services, Inc.

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