Cable and electrical system maintenace
The aim of the article is to give an overview of what is actually happening on the electrical side of your system and how to protect both the system and your earning potential.
The importance of maintaining DI resin and RO membranes is well accepted.
There is however a tendency to take for granted the electrical side of a system and its impact on earning potential. Getting the electrics wrong may just mean a blown fuse but in rare cases it can mean something more serious.
I want to address the myth that simply fitting a higher rated fuse solves the issue and why this is a bad idea, together with the impact of worn cables, the effect of volt drop and cables that are too long. In addition, I want to look at the importance of correct fuse rating, running temperatures of pumps, connectors, controllers and how, as manufacturers, we protect both you and the systems.
The battery state, in terms of maintenance, stored charge, the condition of plates and terminals can play a part in making your system efficient or not.
Earning potential and maintenance of your system are directly related. A well-maintained system will be more efficient, break down less often and can provide a long-term return on investment.
The Battery
The battery is providing all the power needs for your system. As a general rule, you will need a minimum of 75 Ahr (amp hours) for a single pump system and 110 AH for a two pump system.
A fully charged battery is capable of storing up to 14V. For WFP needs, the battery should have a start voltage of around 13V to give you a full days use. It is worth noting that a battery can lose up to 5% of its charge just sitting unconnected. For this reason, it is worth investing in an intelligent charger so if the battery is sat idle for an extended period of time, both volts and amps are maintained.
I am often asked how fast will my battery discharge? There is no simple answer to this as a number of factors come into play, for example:
- Age of the pump
- Pump motor efficiency
- Battery condition
- Wiring condition
- Volt drop
- Water flow rate
- Restrictions in the system
As an example, lets assume we have a one pump system with a well maintained 75 AH battery which starts with 13 volts and full amps. The controller is calibrated to 35 and flow of 60. Based on testing that I have undertaken, the pump will draw around 3 amps an hour, so over 8 hours you are using 24 amps.
Should you choose not to charge the battery at the end of day one, the starting amps availability for our 75AH battery would be 51 amps available at the start of day two, the equivalent of approx 4 hours use.
Battery manufacturers advise you should not deplete a battery below 10.5 volts or 50% of the amp capacity on a regular basis ( e.g. 37.5 amps with our 75AH example). Our battery will need a charge after approx 12 hours use ( 3a x 12hrs = 36 amps used). Draining a battery below the 50% threshold on a regular basis will damage the battery cells ability to hold a charge due to sulphation of the cells.
Most batteries are made up of either three or six 2V cells. Each cell we have a lead plate in it with a sulphur liquid.
To create a current, a chemical reaction takes place between the lead cell and Sulphur acid. As current is drawn from the battery the sulphur residue begins to coat the plate. The more capacity is drained the greater the effect. With repeated cycles this can crystallize and harden. It is this crystallization that reduces the ability of the battery to hold a charge.
Fitting a split charge relay system can help, but this will not replace all the amps you use in a day. It is important to remember the alternator will only trickle charge the leisure battery. The amount of amps that are replaced is dependent on:
- The length of time the engine is running;
- The speed of the alternator;
- The generation capacity of your alternator;
- Other systems operating on your vehicle.
Fitting a larger (100 AH) battery will extend time between charges - in our example the battery will need fully recharging after 16 hours use ( 2 days at 24 amps a day)
Remember, as amps are drawn from the battery, voltage will also fall. In a good condition, as the battery comes under load (pump running) volts will drop by as much as 0.5 of a volt, the voltage will level out here for perhaps 4 – 5 hours; after which you see the volts drop away slightly; after perhaps 6 – 7 hours use the voltage fall away dramatically
Operating a pump without a controller will mean current draw can be up to 9 amps per hour with no significant increase in water flow. This will mean the battery will need charging more often, shortening the life of the battery.
Pump
Different pumps have varying output ranges by this I mean you could set two pumps to the same flow rates with both drawing similar current, One pump is likely to generate more flow and pressure than the other. EG a new pump will out perform an older worn pump.
Your pump is pulling 99% of the current drawn from the battery, the control is using a small amount to operate the processor perhaps 0.1 of an amp.
As the pump reaches the end of its useful life the motor becomes less able to push water, a sign of this may be you having to turn flow up much higher than usual.
The less efficient the pump motor is, the more current is turned into heat as opposed to pushing water. The hotter the motor gets the more current is turned into heat. The temptation to overcome a worn pump and poor flow is to increase the flow setting on the control. This in fact makes the problem worse as the pump tries to draw ever more current which generates ever more heat.
In a recent test running an Aquatec pump flat out (flow and calibration set to 99) temperature levelled out at 70C after an hour. In normal operation I would not expect a the pump to be run so hard as the idea of a controller is to get the pump to produce only the water required, hence a pump is unlikely to get so hot. Some heat generation is unavoidable due to friction, magnetic losses of the motor brushes turning.
Note: A controller can help reduce the operating temperature of a pump as the control reduces the speed the motor can turn at.
On replacing your pump checking the cables and fuse is a good idea replace anything that is worn damaged or rusted. Remember your new pump will be more efficient than the old one so recalibrate the control and in some cases you may find the need to adjust water flow rates.
Cables and Connectors
We supply 1mm tri-rated cable with an 18 amp current rating, the charger controller has 2.5mm cable also rated to 18 amp.
Copper is a good conductor of electrical current however it is not 100% efficient copper will also act as a resistor to current this means a small amount of energy is lost as it passes along the cable, Commonly referred to as volt drop. For this reason all cables should be as short as possible. A longer cable run than necessary can increase the effect of volt drop along the cable length.
Connectors and terminal blocks can also be a source of volt drop for this reason regularly inspecting your connectors replacing any that are worn or damaged is a good idea. Also check connections are secure with good contact to the copper core.
Check for any damaged cable where insulation has been chaffed exposing the copper core not only is there a risk of a short knocking out the fuse the exposed core can be a source of volt drop and become very hot in some circumstance,s this heat can be sufficient to melt insulation and fuse increasing the risk of fire.
An Issue with old connectors is corrosion something that is difficult to avoid in a wet environment such as WFP so keeping connections as dry as possible by placing cable into conduit is a good idea. Corrosion will increase the resistance of the connector and in turn volt drop across the connector.
A badly worn or corroded connector can become an energy wasting resistor. If your connectors are excessively hot they either need replacing or tightening, as your are wasting precious battery power.
The harder the pump works, the more current will be drawn. With poor connections in a system this will increase the energy lost in heat. Because Power = I*I*R (current squared multiplied by the connector's resistance). So the power lost in a bad connector is actually increasing exponentially. Compared to the energy consumed by the pump this is small. But every little helps!
A good connector should only feel warm to the touch in normal use.
Note: The controller carries out an electrical test to ensure the pump and pressure switch are in the circuit. If the pump can not detect the pump due to damaged cable/connectors the control will display PS (pressure switch) as a default message. This is one of the crucial protections we put in place. The control no longer passes any current to the pump but instead retests the condition every few seconds. This prevents a dangerous condition occurring for example ( a loose moving or damaged connection touching ground (Van panels) because the controller is now limiting the energy.
Fuse
All electrical systems should be fused to provide protection to the equipment and cabling. A fuse is a thermal device reacting to heat created in a short circuit and or high current. Not fitting a fuse could mean that a fault situation progressively gets worse. For example if your pump,battery,cables or controller develops a fault or is old a component can go short circuit. With no fuse to open and stop current the component will just get hotter and hotter in rare cases this can cause a fuse, cables to smoke.
You should never exceed the fuse rating advised by the manufacturer. For a fuse to open in a fault condition almost instantly (a few hundred milliseconds ) it can require current of 2.2 to 3 times the rating of the fuse. We recommend 7.5 amp fuses so the actual current to open the fuse may be as high as 22.5 amps.
Over rating the fuse is dangerous.
For example a 15 amp fuse will happily supply current up to 15 amps but will not blow. (to blow it could require current of up to 45 amps) The fuse will however gradually get hot over time in testing I have seen a 7.5 amp fuse heat to 62C and not blow
Imaging just how hot a 15 or 20 amp fuse could get with a fault condition that creates heat but not enough to clear the fuse!!! add in poor cables and connectors and the risk of fire in the cables is increased.
Note: In very rare cases if current is only slightly above or close to the rating of the fuse for prolonged periods there is not sufficient heat or current to blow the fuse, in this case the heat can build up and cause the fuse to melt. For this reason alone you should never over rate the fuse
If a fuse has blown due to a fault the fuse is doing its job.
Please locate the source of the fault and rectify it before replacing the fuse.
Please do not simply fit a larger fuse As above this means even higher current will be required to open the fuse If the fault is a short circuit all you are doing is heating the fault to a point where it could begin to burn
YOU HAVE BEEN WARNED.
The fuse should be as close to the battery as possible. To reduce the risk of over heating in either the cable or device in the event of an electrical fault. The shorter distance current can travel between the battery and fuse means that the amount of cable being protected is increased.
For example, Should the insulation on the red (positive) cable become chaffed allowing the core or poorly installed cable to come into contact with the chassis creating a fault condition .
Without a fuse fitted close to the battery, the wire will heat to red hot, burn off all the insulation and potentially cause a fire.
Fitting a fuse close to the battery protects the cable run plus control and pump.
Another example: Should a control develop a fault in its power circuitry then you must rely on the fuse to protect the wiring. With the fuse fitted close to the controller, however, it would only protect the short length of wire into the controller itself.
Fitting the fuse as close to the power source as possible offers the maximum level of protection.
We also suggest you fit cable in conduit to give two layers of protection to the cable core.
Can I fit two fuses in line?
Why not fit fuses in line one at the battery and one at the controller?
In larger installations the way this is usually done is the fuse ratings increases the nearer you get to the power source. So you could fit a 7.5 amp at the control and 10 amp at the battery.
There is nothing wrong with doing this. It means that any controller faults are protected by the 7.5 amp fuse and the wiring from the battery to the control fuse is protected by the 10 amp fuse. As the wiring is rated to 18 amps this is fine.
In addition, the 10 amp fuse will have a lower volt drop. Then a 7.5 amp fuse.
Fitting two 7.5 amp fuses would mean that you would not know which fuse will blow first. It would likely be the one near the battery due to higher volts here.
Do not fit fuses in parallel as this double the rating of the fuse IE 15 amps if two 7.5 amps fuses are fitted.
The Morale of this lesson is If you are not sure Check the user installation guide or with the manufacturer.
Controller
I have in the past covered how a controller can add value to you system and very quickly return the cost on investment.
As with many things, not all controls are created equal. The Spring range of controllers has a number of unique protection systems built in. These are there to protect the control, system and you the user.
If your pump develops a fault then the controller offers the first level of protection. With a Spring controller if the pump becomes disconnected the controller shows 'PS' because it appears the same to the controller as if the pressure switch has opened. Crucially the controller will not continue to drive current at full power to the pump, but re-test every few seconds. This minimises the risk of a dangerous fault developing (as could occur from a loose/moving connection touching down to earth) because the controller is limiting the energy.
If the pump takes too much current the controller will shut down. A pump may take too much current if it becomes faulty. Alternatively, too much current will be drawn if the pump negative wire should short to earth. In this instance, the controller will shut down the output to protect itself and the wiring. It will display the message 'OC' to indicate this.
Reverse polarity protection
We fit a reverse polarity diode to the power supply circuit on the PCB. The diode is fitted so that in the event of a miss-wire (reverse polarity) it will blow. In this way we are able to protect the sensitive parts of the control and effect a repair if needed. We see a handful of controls come back to us having been miss-ired in any one year.
Fitting a correctly rated fuse will provide additional protection to the control in reverse polarity situation. As the current passes the wrong way around the circuit with the fuse now on the output part of the circuit, it will still blow helping to prevent further damage to the control.
Heat Protection
As previously mentioned copper is not a perfect conductor of electrical current. A small amount of current will be turned into heat, you will notice the pump motor, cables and controller can be warm to the touch after a days use.
The Spring range of controllers is designed to return unused current back the battery and also have a means of dissipating heat to prevent access temperature build up on the PCB.
In testing, we push the control to extremes well beyond that seen in normal use.
Our controllers are able to operate in ambient air temperature up to 40C. By this, I mean that the control will operate normally even if the air temperature during the day reaches 40C. The control will also operate happily in temperatures to minus 5c. Electronics are far better coping with cold than heat.
As part of our testing, a control was fitted to a pump running at maximum for long periods the Temperature of the Control enclosure did not exceed 52C with the internal PCB temperature being 81C.
These temperatures are far in access of what would be seen in a system. For a control to begin to melt temperature would have to be well above 300C at this point the PCB may begin to smoke However it will not flame. In other words this is the equivalent of placing the controller in your oven and turning temperature to maximum.
Note: It should be said that simply fitting the correct rated fuse will avoid any possibility of current feeding a fault condition to these extreme temperatures.
If the Control is experiencing very high temperature it will shut down the pump to protect it self and the system.
Summing up then, we have looked at the importance of correct fusing together with the risks associated with not fitting the fuse. Also, we looked at the power supply (battery) The importance of cable maintenance and replacing worn or damaged connectors.
At Heart Spring is an electronics company following many years testing and development our controllers have a range of self-protection and safety systems built in, that many controls do not. That said the article is aimed at both those who use a controller and those who do not.
As an electronics company development is an evolution so who knows what may come next.
Your safety and ability to earn a return on your investment relies on maintaining and inspecting your system periodically. A few minutes regular maintenance can save you a whole load of problems later.
I hope this article has changed a few miss conceptions and got people thinking.
Be safe out there and if your not sure please ask.