Dimmer Switch For March Pump Speed Control...

[domonsura]

Further to Tony (I think) showing a little dimmer type switch to control speed on his March Pump, guess what i found at IKEA today.... a little in-line dimmer switch that would do the trick for $12.95.
Have attached it to the pump and gave it a go, seems to work well, slide goes from 'OFF' to 'FULL', and seems to have enough adjustment for what we would need. Specs on the switch say it will handle up to 300W, but not sure what amp load it would take.

Simple as plug it into the wall, plug the pump lead into the 'in' plug, and away you go...the dimmer bit is on an extension so is very handy, could be attached forther up your brewstand for convenient access without having to bend over to the pump (which is what i was trying to achieve.)
Maybe not quite as much adjustment as the little switch Tony had, but it would do the trick and is 'Ready to go".

Can be found in the lighting section of the 'market' part of IKEA.

 

[Sammus]

Will handle up to 300W, not sure what amp load it would take though.

Correct me if im wrong but Power = Voltage x Current. So at 240V, it would handle 300/240 = 1.25A. I would have thought the march pump would draw much more than that though?

 

[domonsura]

Dunno mate, not a sparky so I don't know much about that- but it seems to run the pump fine on the face of it - I'm more of a 'plug it in and see if it works' type of bloke........if your predictions are right though, maybe it won't survive a brew,..........
Oh well.......was worth a thought I spose, I'll update when I d a brew then.

 

[domonsura]

I just went out and had another play with it Sammus (you made me paranoid), and it seems to work fine, no issues, the dimmer doesn't seem to get warm at all and the pump runs fine. But you had me worried, can any sparkies enlighten me on whether this would be dangerous? Doesn't seem to be, but then again don't want to get me or anyone else electrocuted.......
To be fair, it does say 'for incandescent loads only' but well......half the things we use were never intended for what we use them for, I figure this is one of those cases......

 

[Wortgames]

I think you run a high risk of burning out your motor by doing this unfortunately. Most AC motors (especially brushless ones, which I believe March pumps are) don't take kindly at all to being run at slower speeds. The current draw can shoot up as the motor tries desperately to stay in sync with the AC cycle, and as a result the coils can fry themselves.

If you need to control the flow just restrict the output, the magnetic drive means you won't bother the motor by doing that.

 

[domonsura]

Also something I wondered about WG, thanks for confirming that for me.....
$250 pump vs $13 dimmer switch? No competition.
Scrap all my clever ideas campers, not worth the risk of killing the pump.

Wonder what else I can use the dimmer for? Guess it's going on the bedside lamp !

 

[Wortgames]

I'm not saying for sure, some AC motors can behave OK at 'throttled' voltages (eg ceiling fans), but most don't - and especially at very low speeds. I think ceiling fan controllers are designed not to output voltages which are too low, not sure whether the fan motors are special or just 'rugged enough' to handle the stress.

It might be worth contacting March and asking them, but I suspect their answer will be 'don't do it, just restrict the output' as that's essentially their intended mode of operation.

 

[berazafi]

DO NOT DO THIS YOU WILL EVENTUALLY BLOW UP YOUR MOTOR (no electric control)

Nice idea though, you would be better to find some sort of electric flow control, which may be avalible cheap

 

[domonsura]

Not sure which one you're saying not to do Berazafi, don't restrict the output of the pump, or don't use electric dimmer device to control flow?
Restricting the liquid flow at the output of the pump is fine, I've been doing it since I had the pump(so have most others), and that's what the distributor recommends, so I'll assume you mean don't use the dimmer option (which I'm not going to anymore)

 

[berazafi]

No electric control will limit this motor safely, i have edited my post. Yes post output restriction is fine

 

[domonsura]

COOL bananas

 

[oldbugman]

unless you put a valve and actuator out the discharge to the pump.

But turning a valve to a set position is pretty easy.

 

[roger mellie]

Shoot me down if you like - but I see no problem with this at all.

Dimmer switches dont reduce the voltage much. Modern type dimmer switches regulate the energy flow by chopping the AC sine wave up and reducing the available energy.

In fact I would have thought that as long as your march pump wasnt stalled and you could start it on full speed then a light dimmer - provided that it was rated for the Full Load Current of the march pump would regulate the speed well.

Of course I dont have this issue with my Perestaltic Pump

RM

 

[mobrien]

now take all this with a grain of salt - I'm not a sparky, just remembering back to my uni physics days.

As I recall, a dimmer works by choppig the AC wave. Effectively, every cycle gets turned of for x amount of time, the x being controlled by the dimmer knob. The lower the "dim" the longer each cycle that the power is off. Now this is fine for a light (incandescent) - the element doesn't have time to cool down too much when the cycle is 50 times a second. However obviously it doesn't work with fluros (or compact fluros).

Now AC motors don't really like being turned off and on all the time - likewise for larger heating loads. So a dimmer is probably not the go.

If you really want to control the motor using an electric system, I suspect that a variac would be the go. A variac is actually a VARIable AC transformer. Instead of chopping the length of the wave, it has a transformer that reduces the height of the wave (i.e. voltage). These I imagine would be fine on an AC motor, as the wave period stays the same (its not chopped up) and the motor is on all the time - its just the voltage (amount of energy) that is reduced. These are a lot more expensive than a dimmer switch though, and you would need to ensure it has a load rating suitable for the pump.

Please correct me if I am wrong - this is remembering back a while now!

M

 

[Wortgames]

The best way to control the speed of any AC motor is with a frequency inverter. Most AC motors are designed to rotate in syncronisation with the frequency of the AC power supply. To reliably change the speed of the motor requires changing the AC frequency. Otherwise, any slowing of the motor will result in constant 'slipping'.

There is a certain amount of slip whenever a load is placed on the motor - in other words, the motor 'slips' out of the magnetic field it was in, and loses a portion of a revolution until it slots into the next magnetic field to come round. However, it initially tries to keep up with its original field by sucking more power. If you are restricting the available volts (or chopping the waveform), then the current will shoot up.

Most motors can handle a bit of this, especially if they have a bit of a flywheel to help maintain momentum. Obviously it happens to any motor at startup and under load, but you are generally talking about short periods of time and limited deviation from optimum. A light dimmer however will happily pass ridiculously low voltages for as long as you like.

If the motor's coils aren't built to handle the higher current they will quickly begin to deteriorate, and once that happens they will soon cascade into destruction. Another point to remember is that inductive loads don't really like sudden current spikes and as a result weird things can happen to the voltage, possibly frying the dimmer, which could result in who knows what going to the motor.

I would do a lot more research, and speak to the manufacturer, if you want to electronically control the speed of the pump motor. I certainly wouldn't just do it with a cheap lamp dimmer unless you were prepared to take the risk of losing both the motor and the dimmer. I really don't see any advantage in taking this risk, as these pumps will quite happily run all day with the output completely blocked if you want. So it seems a much better option to let the motor do its thing naturally and play with the output instead.

 

[domonsura]

Yeah, I have just been restricting the output of the pump up until now, I'll just continue to do that. Not willing to risk my pump for some temporary convenience
Dimmer switch relegated to bedside lamp........(mood lighting also has it's advantages in making up for many un-approved recent brewing purchases..... )

 

[nifty]

Yeah, I have just been restricting the output of the pump up until now, I'll just continue to do that. Not willing to risk my pump for some temporary convenience
Dimmer switch relegated to bedside lamp........(mood lighting also has it's advantages in making up for many un-approved recent brewing purchases..... )

Hi domonsura

I use the exact same dimmer for my stir plate. It's been working well for the last 12 or so months.

cheers
nifty

 

[domonsura]

Awwwwwwww man, NOW I need a stir plate.........

 

[Tony]

I am going to try and get mine hooked up tonight.

I will take some current readings in normal full speed mode pumping water in my system and with the speed controller hooked up.

I am an elecrician by trade and working as an electrical control systems engineer ATM. I think most of the problem with AC motors overheating is due to their cooling systems being rated for them running at full speed. Once you slow them down, they can still draw the same current and produce the same heat, but you get bugger all cooling air passing over them and the internal windings and they can over heat.

Industrial Variable Speed Drives, as said before, reduce the frequency which slows the rotation of the magnetic field in the motors stator. The rotor follows this Stator magnetic field so in turn the shaft rotation speed is reduced. These drives do not put out a simple sine wave though. they usually use a kind of square wave output that can change shape if you ask for different torque requirements for different applications in the settings of the drive.

I have never seen an AC motor burn out from the use of a variable speed drive. I have seen them overheat when being run below 15% of their rated speed but we just put bug cooling fan on it that rann at full speed all the time.

They actually last longer if anything

I will post my results if i get to it

cheers

 

[domonsura]

So Tony, what would your take on this little cheapy dimmer be? Don't do it?