50A SSR Problem

[abltech]

I have a problem with a 50A Solid State Relay - the output on side 1 is fine at 230V however the output on side 2 when switched is only 120V. The load is two heating elements. First thing I did was change the relay for a new one but the funny thing is when I install a new relay I get nothing coming from side 2 when switched? (I tried two brand new relays both like for like with the one installed before).

This means that the elements are only getting half power and are not generating the correct heat for the warming bin.

Would appreciate any ideas anyone has.

 

[Darkwood]

What controls the SSR are you sure you dont have a 0-10v analogue control burst firing system to vary the output power acting like a temp' control?

Have a read up on SSR control its really the wrong approach to change things that you dont understand fully as it may cost you or your customer when it is not faulty to start with SSR are not hard to learn and read up on but its essential the correct one is selected for each situation... heres a link to describe what im suggesting with burst firing of the control.... ideal for resistive elements and heat control.http://www.newark.com/pdfs/techarticles/crydom/OutputSwitchingSSRs.pdf

 

[abltech]

The relay is a Crydom D2450 which is a synchronous relay - it does not allow burst fire or proportional control. The input comes from a MTR6 controller that gives a 24V DC output when the temp probe reads less than 66 deg. I should also say that I have spares of these relays in the van and took them out to see if that was the problem just for process of elimination - certainly didn't charge the customer for them.

I really am puzzled by this one - also thanks for the pdf it has some good information in that.

 

[Darkwood]

Sorry wasn't try to teach you to suck eggs here thought you were trying to resolve a problem with lack of knowledge but checked your profile and clearly you are working in the field you trained in... thought you were an Electrician expanding his horizons...

With the extra info you supplied it does seem a head scratcher the first thing i would do is lash up the SSR to a direct 24v dc supply from a seperate source to see if your DC supply is corrupted and giving a pulse train output as opposed to a steady supply taking the thermostat and controller out of the loop would be my first port of call. Let us know if you identify the issue as its not one ive come across and always good to know to add to the brain bank.

 

[abltech]

You won't finding me knocking any information - I will come back to you tomorrow and let you know who I get on.

 

[Knobhead]

As usual I’ve arrived late.

Please let us know how you go on with this.
I’ve always found SSR’s to be very reliable. I used to use them on quite high reactive loads and so I doubled the O/P rating. In 30 years I don’t think I had one fail.

 

[Gage]

Pid :33:

 

[malcoa]

It looks like the MTR6 is relay output from the data i can find and the relay is just a simple ssr, i would hazard a guess that there is something wrong at the element end but i'm guessing that thats all been checked, out of interest have you tried swapping the outputs(elements over)?

 

[Knobhead]

Pid :33:

What’s Process Inverse Derivative got to do with it? Other than my response had a too high lag time.

 

[netblindpaul]

Proportional, integral, derivative Tony!

 

[Gage]

What’s Process Inverse Derivative got to do with it? Other than my response had a too high lag time.

As above lol.

And well as I've been itching to mention it for a while I thought this thread could possibly sway that way (wishful thinking). OH WELL.

 

[Knobhead]

Proportional, integral, derivative Tony!

Brain out of the loop :sad:

Don't know how I cocked that up. I've used it enough times on PLC's.

 

[Darkwood]

You won't finding me knocking any information - I will come back to you tomorrow and let you know who I get on.

Its tomorrow abltech .....any feedback as its an interesting problem you have there!

 

[johnboy6083]

Sorry to jump in, but does anyone have any simulation software for PID control. It's a subject that we haven't covered on my HNC (even though weirdly I'm one assignment away from a distinction in this module).
It's something I'd like to understand fully, not just the textbook version of how they're supposed to work.

 

[abltech]

Well, after being back on site I have found there is continuity between the load supply and the output wire to the element without the relay connected. There is also slight continuity between L-E (and hence TN-C-S slight continuity barely readable with earth). I could not fully isolate the unit today to test as it is installed in a 24hr McDonalds that has a load of other appliances running off the circuit which they could not afford to go down and at the moment the elements are giving out 52 degrees which is not quite the 66 set point, but they would rather have that than me turn it off for 30mins!!

However all that said if the relay is bypassed and supply to load is connected directly then the elements heat correctly which I was expecting anyhow. The controller is definitely fine - it gives out a steady 24VDC supply and energises and de-energises the load upon the correct input signals.

This leads me to believe there is an insulation problem somewhere along spaghetti junction - but still does not explain why this one relay gives out 120V with the fault and a brand new replacement gives out 0V. The relay which I did remove and tested works perfectly well on the bench.

I suppose there could still be a faulty element - just because it heats doesn't mean it isn't leaking somewhere.

My heads melted with this now!