[[GQC] Tim]

I've got the Digital Varistream, and everything seems to be going great, good flow, no weird things, except one.

I don't know if it's normal or not.

The digital varistream hits the shut off pressure, red light shows for less then a second, on comes the green light, and a high tone increasing in pitch for about a second starts, and then the light turns red again, this goes on and on. I wonder if that is normal.

When do you know if you have to change the shut off pressure setting? I have absolutely no idea.

I've got a Numatic trigger on the pole, 100 PSI Shurflo pump, 100m minibore, don't know if that helps. A couple of seconds after I press it, the pump starts pumping, and when I stop the trigger, the pump flows a bit more for a couple of seconds, and then hits the red light, and the increasing high pitch tone starts again when light is green, then the red light is on again for less then a second. You get the point.

Please explain what the shut off pressure thing is.

[[GQC] Tim]

Anyone?

[michael papworth]

Hi Tim, What you describe is the same as I observe, so I guess it's normal. As to how it works, this is a question that has puzzled me for a while. It took me ages to fit mine precisely for this reason. I HATE working when I don't really understand what's going on, and I couldn't understand HOW it worked.

Well, I've given it a bit of thought since then and here's my best guess.

A bit of physics to start with:

An electric motor and a generator are essentially the same thing. In a motor, you put electrical energy in and get mechanical energy out. In a generator, it's the opposite. When you power up a motor, it produces what is called a back voltage. This back voltage depends only on the speed of the motor.

The actual voltage that the motor "sees" is the difference between the input voltage and the back voltage. When a motor slows due to too much load, what happens is that the back voltage goes down to zero and too much voltage (and hence current) goes into the windings, heats it up and burns it out.

The varistream does two things:

1 - it stops the pump when the pressure builds up and

2 - it starts the pump again when the pressure drops.

What I guess happens is that the varistream monitors the back voltage and cuts out when it falls due to pressure building up and slowing the motor down.

How it starts the pump again is a bit of a mystery. What I guess happens is that when the pressure drops, the diaphragm in the pump moves and this movement is fed back to the motor which produces a back voltage that tells the varistream to start again.

All that sounds a bit like science fiction to me, but I really can't come up with anything better - and I've thought about this for a while.

If anyone has a better idea, I'd love to hear it.

[[GQC] Tim]

Yea that makes sense, another thing I heard is that it monitors the amperage drawn by the pump.

I'll have a proper fiddle today. See how it works.

[michael papworth]

Yes, that's right.

Sorry about this, but there is no such thing as amperage. The word is current. Ampere (always with a capital A) is the unit of current and the spoken abreviation is Amp and the written abreviation is A, so we talk about a 13 Amp fuse but read or write about a 13A fuse.

When the back voltage falls, the current in the windings of the pump will rise. That part is pretty clear. The varistream must monitor either current or voltage. I'm not sufficiently up on electronics to know which is easier or more reliable to measure - I suspect that it might be the voltage. To be honest, for our purposes it's not really important.

Of course, the other thing that the varistream does is to control the voltage going to the pump so it pumps at the rate that you want.

The real question is how it knows how to start again. That (to me) is the scary bit as it's a bit too much like magic!!!

Love your questions. You ask some really interesting (to me) stuff. We must be soul buddies.

[[GQC] Tim]

Hm, yea they are interesting little things.

I just wonder when you know that you need to change the varistreams shut off pressure? Everything seems fine to me lol, it pumps well, no pulsating things.

Would be nice if somebody who knows how to set that up would post here.

[Xline Systems]

you can alter the pressure setting easly. do you have any paperwork with the varistream it should tell you on there. if not i can email it you

[[GQC] Tim]

you can alter the pressure setting easly. do you have any paperwork with the varistream it should tell you on there. if not i can email it you

I know how to change it, I just don't know when or if you need to change it.

[TERRY AB]

Hm, yea they are interesting little things.

I just wonder when you know that you need to change the varistreams shut off pressure? Everything seems fine to me lol, it pumps well, no pulsating things.

Would be nice if somebody who knows how to set that up would post here.

The shut off pressure only needs adjusting when the varistream doesnt shut off early enough or too late, creating too much pressure in your hoses/or not enough, which could cause the fittings/hoses to bulge/blow off. On a 100 psi pump the original setting should be perfect, the adjustments are for users with a different pump or setup. To adjust you need to read the manual. It is a case of pressing the up and down buttons (at the same time) for 3 seconds letting go and then doing this again for a second, the display will then show the shut off pressure in the display, you can then adjust this, again by touching the up or down button until you have a correct setting, then turning the pump off and on again. Hope this is correct, quoting from memory.

[[GQC] Tim]

Hm, yea they are interesting little things.

I just wonder when you know that you need to change the varistreams shut off pressure? Everything seems fine to me lol, it pumps well, no pulsating things.

Would be nice if somebody who knows how to set that up would post here.

The shut off pressure only needs adjusting when the varistream doesnt shut off early enough or too late, creating too much pressure in your hoses/or not enough, which could cause the fittings/hoses to bulge/blow off. On a 100 psi pump the original setting should be perfect, the adjustments are for users with a different pump or setup. To adjust you need to read the manual. It is a case of pressing the up and down buttons (at the same time) for 3 seconds letting go and then doing this again for a second, the display will then show the shut off pressure in the display, you can then adjust this, again by touching the up or down button until you have a correct setting, then turning the pump off and on again. Hope this is correct, quoting from memory.

What is normal for a Varistream? When is it supposed to turn off? I don't have connectors blowing off, so I can't go by that.

[Xline Systems]

working fine tim dont panic. 

[[GQC] Tim]

Okay cool. I'm glad I don't have any problems with it, after so many people did have problems with it, maybe it's all fixed with the digital one.

I'd still like to know (to increase my knowledge, and if I ever need to help somebody out on here), when you change those settings,