6 Ways to Reduce Electrostatic Damage to Control Boards
When we first learned how to change a control board on a furnace, we were educated by professionals to take great care and remove any static from ourselves before removing the board from the box.
If we are careless, we could damage the control board before the furnace even ran for the first time after the repair.
It’s called electrostatic discharge and it’s a bigger problem with modern electronics than it’s ever been. About a third of all control board failures come from damage caused by electrostatic discharge.
You might have seen those pristine labs where they manufacture control boards. One of the main goals of those rooms is to reduce static.
Once a control board is created, it’s prone to static damage.
If damages were to happen at the lab, the cost to manufacture another one is very little.
But if the damage happens during testing, it requires 10 times the cost to make it.
And if that board fails at the customer’s house, it takes a hundred times the cost to manufacture a new board at the lab – package and ship it to an HVAC warehouse, ship it to the HVAC contractor, who then drives to the customer’s house and has it ready for the customer to replace it and put a warranty on it.
When it comes to static damage to a control board, it’s not so much about the voltage being transferred from you to the metallic parts of the board itself, but more about the resistance incurred as it travels through the pins, transistors and other parts of the board along its way to the path to ground.
You’ve seen those big controls and relays that were used on decades-old furnaces, they’re the same controls used today to direct the sequence of events that start the furnace and shut it down.
Anyone who has worked on an old furnace could tell you those relays and switches take up a lot of space in the control panel.
These days all those relays, transistors, and switches have been shrunk down to the point that they now fit on a printed control board – the size of a small envelope.
Those old relays and controls being larger than today’s parts were constructed with heavier materials, that’s why they’re more durable over time.
The strength of the materials used to build small control boards is not going to be as durable as those bigger, heavier parts.
You know the saying “They don’t make them like they used to?” Well, there is something to that.
A static discharge 20 years ago would have been harmless to those controls. Today, that same discharge through the board can result in catastrophic damage.
Transistors are often the victim of a static shock to a control board, but pins, brittle solder, and the silicon itself can be deformed by the heat that travels through during a static discharge.
Damage like this can make a control for the blower motor which is supposed to be off at a given time – to a blower that’s always on now, or a safety switch that’s normally closed to become constantly open.
These parts of the furnace that are needed to work in a certain order can be thrown out of whack very quickly with the slightest arc from your body to the control board.
Most people don’t even know they’re charged with static electricity as they cross the carpet floors, and onto the HVAC system of a customer’s house until they feel the spark travel from their fingers to the brand-new control board they’re changing.
Some of those technicians also don’t know they’ve just damaged that expensive control board, their customers are getting ready to pay for.
You don’t have to be wearing a flannel shirt and your favorite pair of woolly socks to develop static.
Although clothing like that, as well as other situations, can create a significantly higher amount of energy than the body can store which will need to be discharged at the next available piece of metal you touch.
Suppose you were out on preventive maintenance or a service call doing a visual check of the backside of the control board. We all know the solder connections are on the back of those boards, which are receptors for Molex plug connections that control many of the basic functions of the furnace.
Well, heat from a minuscule 24 volts, over time, will fracture those solder connections, which is why we inspect the back of those boards regularly in the first place.
But if we bring with us a body full of static and touch that control board, we can create a very minor defect in the board, or make a preexisting, undetected condition even worse.
All of these just break down the control board over time until it completely fails.
Every control board we’ve ever changed was stored in an anti-static bag, which comes inside a control board box.
Even those anti-static bags are conductive, but they do help reduce and negate any static electricity the board might encounter during shipping, and riding around in the back of your truck.
So, what can we do to prevent ourselves from damaging printed circuit boards in the future?
Here are what you must do.
#1. Both Hands Touch the Furnace.
Ground yourself to the furnace before touching the delicate components inside of them, something that has a direct path to earth.
When we ground ourselves, we’re removing any excess voltage that we may have created and carried with ourselves as we walk to the furnace.
#2. Avoid Carpeted Work Spaces
Try working in an area where you’re not standing on carpet or area rugs.
These will encourage you to generate static, even after you’ve already grounded yourself to the unit the first time.
A canvas drop cloth is a lot less likely to generate that same static and working on concrete or bare floors is even more ideal.
#3. Humidity Levels.
We know you can’t change this while you’re servicing the HVAC system but having an understanding of the humidity levels in the room can help too.
A room that has 40 to 50 % humidity is less likely than a dryer room to encourage static.
#4. Unplug the Furnace.
You want to make sure you’ve unplugged the furnace.
Make sure that no electrical currents are running through the system.
#5. Only Touch the Sides of the Board.
When you do take the control board out of the anti-static bag, or when you remove one from the furnace to inspect it, make sure you’re only touching the sides of the board.
A voltage potential is conducted through all the metallic parts of the board. These are the areas that you don’t want to have your fingers all over.
#6. Stay Hydrated.
Speaking of hands, keeping your skin moisturized by drinking plenty of water, and even using lotion will help keep static electricity down. Dry skin encourages static to build up even after you’ve grounded yourself the first time.
You’re not off the hook as far as static discharge goes, so grounding yourself to the furnace multiple times isn’t unheard of.
And here’s a little tip. Want to reduce the chance of that painful snap between you and the metallic object you choose to ground yourself to?
Use something like your metallic car keys to touch that ground. This allows the discharge to travel straight through the key instead of straight to your hand.
Well, we hope this helps a little bit and is something that you can use out there in the field as an HVAC technician or as a home DIY’er.
The last thing we want to do is damage something before it even has a chance to do its job, right? Handle today’s electronics a little more carefully than the parts of old, because they’re not as durable today.
If you’re not sure you’re doing the right thing, call one of our techs at Red Deer Heating and AC and we’ll replace the control board in your furnace.