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Stir Plate Questions and Answers

Does your product come with a warranty?

Our stir plates ship with the following warranty and this warranty is in effect regardless of who you bought your stir plate from. Warranty repairs can be handled through the retail outlet you bought your stir plate from or directly through us.

Stir Plate Product Warranty

This product is covered by a one year workmanship defect warranty. Your stir plate warranty extends one year past your purchase date or 18 months from the manufacture date.

To claim your warranty, ship your defective stir plate along with a note explaining the defect and a copy of your purchase receipt to the address listed on the web site. If returned without a valid receipt, the manufacturing date code will be used to determine warranty status. is not responsible for warranty return freight but will cover freight back to you. Repaired and / or replacement product will be returned as shipped to us. For example, a stir plate shipped in without stir bars will be returned without stir bars.

This warranty does not cover user abuse, damage from incorrect power supply or unreasonable product expectations. For example, expecting a SP-2000 to spin a 5 liter starter as well as a SP-3000 spins a 5 liter starter.
Does your stir plate have a weight limit?

Our stir plate housings are made of high impact high strength polystyrene plastic and there is no known weight limit. I've actually stood on one of the assembled housings we use to see if it would hold up to my weight and it did. But like everything else you should be reasonable. You might figure out how to put a 5 gallon carboy of beer on our SP-2000 stir plate, but why?

Does your stir plate have a size limit?

We have set-up a starter in a 5 liter flask on our SP-2000 model stir plate just to see what would happen and the starter spun fine, even though the 5 liter flask overlapped the sides of the stir plate by quite a bit. But the overlap worried me - it just didn't seem safe. This test and requests from customers for a stir plate that would reliably spin a 3 to 5 liter starter led us to design the SP-3000 stir plate. Then during most of the summer of 2011 we worked on the Black MAXX Stir Plate, the only low cost stir plate we know of designed to spin a 5 or 6 gallon carboy of beer.

Here are our recommended flask size ranges for each stir plate:

SP-2000 - 250 ml to 2 liters
SP-3000 - 1 liter to 5 liters (our most flexible stir plate)
Black MAXX - 2 liters to 6 gallons

Do your stirplates come with Speedsafe?

Speedsafe is a term used by a competitor to show that their stir plates will not over-rev and destroy themselves. And although we can't use their term in our product, our stir plates are also RPM limited and will not over-rev and it is perfectly safe to remove a flask from one of our stir plates, even at full RPM.

Does your stirplate make noise?

All stir plates can make noise depending on the RPM you run them at, the type of stir bar you choose, the type of flask or jar you use and how well the flask is centered on the stir plate. The noise is caused by the stir bar wobbling inside the flask and the noise can also be caused by a stir bar that's too long. Our stir plate is no exception, but we carefully chose the correct length stir bar and other components to minimize this effect.

One competitor falsly states that PWM is noisy - it's not. Our stir plate does make a slight humming noise at some speeds - It's inherent in the design of a PWM stirplate. But we chose a PWM frequency and components to minimize the hum and the volume is low enough that you can't hear it over the stir bar. And anyways, you aren't going to be running one on your night stand!

I built a stir plate using one of the LM317 regulator plans on the net. The stir plate spins the stir bar fine at slow speeds but when I try to speed it up the stir bar throws off every time. Did I do something wrong?

Probably not - there are issues with the simple LM-317 design that's floating around the net. The biggest issue is that at anything remotely approaching full speed, the motor is spinning way too fast. A LM-317 regulator based design will work but you need to build a smarter regulator circuit that limits the voltage to the motor to about 6 VDC. Also, no-one discusses magnet spacing in detail and the type of magnets you really need to be using. One of the worse magnets to use is a used hard drive magnet because a used hard drive magnet does not provide the two concentrated magnetic poles you need to keep the stir bar captured at all speeds. Also, because of the shape of a hard drive magnet it's impossible to have the weight centered and the two poles centered. To keep your stir bar captured at all speeds, you need two opposing magnets with a flux density of at least 2500 Gauss, the poles must be under or just outside the ends of the stir bar and the magnets need to be very close to the ends of the stir bar.

Note: Some people try to play down these design flaws by stating something like "you don't need to spin your stir plate at high speed anyway, just a dimple on top will do". This does little to explain away an obvious defect in their design!

Not seeing your stir plate I really cant tell what's going on but maybe I can help anyway.

I'd suggest placing the stir bar in a flask full of water and then lower the flask towards the top of the stir plate. If the magnets don't grab onto and center the stir bar within 1/4" of the top of your stir plate with some force then I can say for certain that your magnets are mounted too far from the top of the box or they are not strong enough.

If the stir bar does center but you can't run full speed then start slow and slowly turn the speed up. If you can generate a vortex that reaches at least 1/4 way down the flask but the stir bar is thrown at faster speeds then the regulator is driving the motor too fast for the magnets.

If you can't generate much of a vortex before throwing the stir bar then it's a magnet problem. The drive magnets aren't strong enough, you are using a used hard drive magnet, the spacing isn't correct (this could be center to center spacing or distance from the top of the box) or the stir bar is bad (not likely).

With any well designed stir plate, you should be able to place your flask on the box, turn the stir plate on, then adjust the speed to high. The stir plate should spin up to full speed and pull a strong vortex without throwing the stir bar.

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Last modified: 2/21/12