Potentiometer 240V Left On Low Harmful?

[NineInchNails]

I recently was running my 5,500W 240V element in my boiler using a SD Potentiometer, SSVR with fan. I was running it for a while, I was about to turn the element off, but turned it all the way down then got distracted for a little while. I smelled that bad electrical odor then switched the controller off. After a while I turned the controller back on and cranked the element to 100%. I noticed my cheapo, China Volt/Amp meter was reading incorrectly, as though it were illuminating excessive number of pixels and didn't display proper numbers.

I opened up the controller and I believe the odor was coming from the cheap, China Volt/Amp meter.

I presume that leaving the Potentiometer on the lowest setting might be the cause, but I recall the Volt/Amp meter not displaying properly just before this happened. Is it bad to leave the Pot on low for extended periods of time or was this just a garbage Volt/Amp meter?

[StillerBoy]

Is it bad to leave the Pot on low for extended periods of time or was this just a garbage Volt/Amp meter?

It's possible that it was a bad v/a meter or it could be in the wiring.. but leaving a pot set at it's lowest lower should not hurt the pot or the meter as it is not connected to the pot..

I've often shut the pots down and not shut off power for a heat brake, and over the years never had an issue.. I've never had an issue with any of the controllers I've built, and my is over 7 yrs of usage on a weekly level..

Also on 240v remember that there is always current running through the element (low level current but still current flow) even with the pot set on the off or lowest setting..

Mars

[NineInchNails]

I bought a new volt/amp meter and it should arrive today. I just thought it was odd that it malfunctioned and smelled somewhat burnt, but only when the Pot was on its lowest setting for a while. When I run the controller normally it doesn't stink. Strange.

[Yummyrum]

NIN , what happened is not new . It is why you will often see that guys wire up these meters so that the Voltage is on the input not the output . It means the meter will always read the supply voltage , not the element voltage , but you just use the current as a guide .

The reason is that these meters need power to operate ( obviously) , and they get this power from the Voltage connection .

At low settings on the SSRVR , the wave form is a series of narrow spikes and to maintain operation , the meters takes more current to operate , it apparently exceeds the limits of the components in the meter power regulator circuit and the smoke is released.

If the meters were working off a true sinewave at the lower voltage , it wouldn’t be a problem .

Note that this is a situation that happens with all SSR VR regulators and is not common to just SDs ones .

It should be possible to hack the meters and provide an external power supply while still being able to monitor the Voltage at the element . But that is nit something I have the time to do these days .

[OtisT]

I bought a new volt/amp meter and it should arrive today. I just thought it was odd that it malfunctioned and smelled somewhat burnt, but only when the Pot was on its lowest setting for a while. When I run the controller normally it doesn't stink. Strange.

It’s possible that the pot is getting hot which can cause it to smell. More resistance, more heat. Who knows if it’s the smell you’re smelling? Maybe try replacing the pot with a higher power rated pot of the same resistance range? Something that can dissipate more heat. Just a theory on getting rid of that smell. Otis

[NineInchNails]

I bought a new volt/amp meter and it should arrive today. I just thought it was odd that it malfunctioned and smelled somewhat burnt, but only when the Pot was on its lowest setting for a while. When I run the controller normally it doesn't stink. Strange.

It’s possible that the pot is getting hot which can cause it to smell. More resistance, more heat. Who knows if it’s the smell you’re smelling? Maybe try replacing the pot with a higher power rated pot of the same resistance range? Something that can dissipate more heat. Just a theory on getting rid of that smell. Otis

I'll be changing out the malfunctioning amp/volt meter today and see how it goes. I have a spare Still Dragon Potentiometer so I could change that out, but I don't have a larger one. I should be able to isolate the stench once I remove the amp/volt meter.

[Yummyrum]

NIN
viewtopic.php?f=85&t=56032#p7318075

[gwizard]

I bought a new volt/amp meter and it should arrive today. I just thought it was odd that it malfunctioned and smelled somewhat burnt, but only when the Pot was on its lowest setting for a while. When I run the controller normally it doesn't stink. Strange.

Have you wired your amp/volt meter AC input before SSVR? Might not contribute to smell, don't know, but might have to do with flickering you mentioned. Mine has 4 wires. 2 for load measurement, meaning live wire goes from SSVR to meter and out to element. The other 2 wires are live and neutral, connected to the main input, after the fuse, but before SSVR.

Hope that's clear enough.

Also, I would check that POT is sufficiently rated. SD one is 2W, which is on the low side. You might consider popping into Jaycar and getting something bigger.

[NineInchNails]

I bought a new volt/amp meter and it should arrive today. I just thought it was odd that it malfunctioned and smelled somewhat burnt, but only when the Pot was on its lowest setting for a while. When I run the controller normally it doesn't stink. Strange.

Have you wired your amp/volt meter AC input before SSVR? Might not contribute to smell, don't know, but might have to do with flickering you mentioned. Mine has 4 wires. 2 for load measurement, meaning live wire goes from SSVR to meter and out to element. The other 2 wires are live and neutral, connected to the main input, after the fuse, but before SSVR.

Hope that's clear enough.

Also, I would check that POT is sufficiently rated. SD one is 2W, which is on the low side. You might consider popping into Jaycar and getting something bigger.

Here's my wiring diagram. Do I have it in the wrong location?

What size potentiometer would you recommend? It's strange that SD would sell the wrong one with a kit they have been selling for many years.

[gwizard]

Here's my wiring diagram. Do I have it in the wrong location?

For some reason I was under impression you're in Aus. The diagram is for US.
Yes, it is in the wrong location, as I suspected.

Change red line input to meter from SSVR leg 2 to leg 1, so it goes directly from your mains, but after fuse.

What size potentiometer would you recommend? It's strange that SD would sell the wrong one with a kit they have been selling for many years.

To be honest, I use SD one myself. But, when I shown my design to my father, who has over 60 years of electronics experience, he commented that it was on the low side.

I think your issue is the AC input to the meter. Leave POT as is.

[gwizard]

Here, I "fixed" your diagram

[NineInchNails]

Here, I "fixed" your diagram

02 CONTROLLER OFF.jpg

Thank you very much for that correction! I'll update the diagram and see how it goes.

[NineInchNails]

I have a feeling that correction you made may be incorrect for the unit I purchased. I attached the instructions. It appears I need to connect a neutral wire and a power wire, not both power wires.

These instructions have me confused.

[NineInchNails]

Nevermind ... I got it. Brain fart and now I understand it.

[Yummyrum]

Nine Inch Nails, Gwizard is trying to tell you the same thing I have been since the start of this topic .

Follow his wiring diagram . Yes I know its not what the instructions say . Yes , the voltage reading will no longer show the actual voltage at the element anymore .....but it wont burn up anymore .

If you look at a lot of builds you will see that it is the way to connect the meter so .... they won’t blow up

[NineInchNails]

Nine Inch Nails, Gwizard is trying to tell you the same thing I have been since the start of this topic .

Follow his wiring diagram . Yes I know its not what the instructions say . Yes , the voltage reading will no longer show the actual voltage at the element anymore .....but it wont burn up anymore .

If you look at a lot of builds you will see that it is the way to connect the meter so .... they won’t blow up

I just wired it like in his diagram. I'm going to take a break, go back out and triple check it before I fire it up.

[NineInchNails]

Well I wired it up like recommended, but it isn't reading watts or kwh. Sorry if I seem brain dead, but it's hot as hell in the garage and I've been out there all day. I suppose this is not a big deal because I have Volts & Amps. The rest is just useless eye candy I guess.

Yummyrum I checked out that thread, but I have not read it entirely to grasp the full point. I will later tonight.

[gwizard]

In that picture, is it running any kind of load? If there is no load, there would be no watts displayed

[NineInchNails]

In that picture, is it running any kind of load? If there is no load, there would be no watts displayed

Yeah it was turned up about half way in that pic. That's why is displays approx 15A.

I thought the issue might be just a setting. The instructions say to enter 'overload power'. I assume that is 5,500W for my element. I entered 5.5 KWh and it still reads zero for watts. Oh well.

[gwizard]

Sorry, mate, your meter is different from mine. Plus, I'm not familiar with American wiring.
Maybe try resetting it? On mine there is a small button.

[jonnys_spirit]

If it shows amps there’s a load or at least amps are flowing across a load. Maybe there’s a setting for Ohms value of the intended load?

Cheers!
-jonny

[Yummyrum]

Curious when you turn it up full , does it then read power ? and does the Power Factor go to 1.0 ?

At full power , the current and voltage waveforms seen by the meter should be close to identical and the meter should show a power reading and Have very close to PF =1.

If not then maybe this meter is a dud . .

Others have used Power/ Volt/ Current meters and they show power when connected as gwizard showed ( however the voltage reading will be always the input voltage )

[NineInchNails]

Curious when you turn it up full , does it then read power ? and does the Power Factor go to 1.0 ?

At full power , the current and voltage waveforms seen by the meter should be close to identical and the meter should show a power reading and Have very close to PF =1.

If not then maybe this meter is a dud . .

Others have used Power/ Volt/ Current meters and they show power when connected as gwizard showed ( however the voltage reading will be always the input voltage )

At full power it displays this. Sorry the pics are upside down. I uploaded from my phone and it just won't work right even when I rotate the pic.

At lowest power it displays this.

[Yummyrum]

Cool , so its thinking there is a PF difference at less than full power because it see’s the difference between the Voltage and current waveforms .(Which although there isn’t really a Power Factor change in a resistance such as an element , it just thinks there is)

I have to say even now , I think your meter is faulty , at full power , there will still be a very slight difference between the input Voltage and the current waveform, but it should not be enough to cause the meter to not display power .


So next thing I would do is swap the wire back to how you originally had it and run it on Full power only .
It should now see exactly the same waveform on both the current and voltage waveforms . It should display power now . If it doesn’t , its definitely a dud .
( don’t turn the power down or it will burn out like your first one did though )

[StillerBoy]

The wiring does not look right to me, but hoping I'm wrong.. there's a breaker missing in the wiring system as it seem to have lots of current flow back..

The line (Black) is wired in such a way the meter donut always has power to it.. and the switch does not seem right how it's wired.. there seem to be always some current flow back..

Plus both SSR are always being fed current one way or the other..

Mars