Solid State relay

[r.bartlett]

Chaps

I have to replace a solid state relay which is woking one phase of a 3 phase heater bank (the other SSR is ok)

The unit is a CG model number CARLO GAVAZZI - RN1A48A50 - SSR, 50A

the details of it are as per pic. My problem is they are on short stock so I wonder if there is anyother one which I could get from RS which would do?

Untitled

• r.bartlett
• 2 Dec 2012
• 1

I assume another manufacturer will work but need expert advice before I go fit

TIA

 

[ricicle]

Any SSR with the correct control voltage range and current carrying capacity will do.

 

[JohnW2]

Looking at the specifications of the SSRs posted in the OP, I think I might struggle to understand a control voltage of "24-230V ± 15%". Does that mean that it would definitely work at 24V, but might not at 195V (!), or what? Is this perhaps a conventional way of expressing control voltages which I'm not familiar with?

Kind Regards, John
Edit: typo corrected "195%" corrected to "195V"

 

[bhm1712]

it means the ''coil'' (not really a coil in SSR but for the purpose of this..) will operate with a voltage of 24 minimum to 230 volt maximum.... its as simple as that. Put 24 volts on the coil and it will switch, but 110v on the coil it will switch. Put 230v on the coil it will switch.

Edit: the +/- 15% is to cater for voltage variations - some 24 volt supplies will be a bit less, or a bit more than 24, as will 230 at the wall. So being pedantic it will operate at 20.4V- 264.5v reliably. It doesnt mean that the in a pack of 10, the coil might work at 230 on some, but only 195 on others. The variation is for the supply voltage not the coil.

 

[bhm1712]

looking at RS theres nothing else which has a control voltage of 230 with a load current of 50A.

Do you know the actual load on the SSR? what power are the heaters?

 

[bhm1712]

RS 231-0848 would do it, but its £143 and is over the spec of the old one.

 

[Iggifer]

RS 171-8948 is very similarly specced to 2310848 and only £30, no integrated heatsink though

 

[bhm1712]

no its not......it has a control voltage of 3 - 30 vdc and a 10 amp max load..... how did you come up with that?

 

[JohnW2]

Edit: the +/- 15% is to cater for voltage variations - some 24 volt supplies will be a bit less, or a bit more than 24, as will 230 at the wall. So being pedantic it will operate at 20.4V- 264.5v reliably.

That's why I was uncertain about the intended interpretation. If they meant that it would operate reliably for control voltages in the range 20.4V - 264.5V, I would have thought they would specify precisely that (as is done for most relays/contactors) - or even, perhaps, "142.45V ± 122.05V". That is why I wondered whether talking about "± 15%" was intended to mean something subtley different (specifying a "±" figure as well as a range is rather unusual - normally one or the other, not both!) ... but it seems not! As I pointed out before, my initial inclination (to read it as "24V ± 15% to 230V ± 15%") just didn't make sense!

Kind Regards, John

 

[bhm1712]

ever since ive been in the industry its always been specified like that on everything which has a variable voltage. From relays to sensors to power supplies.

Its handy that they make stuff like that really....always good in a situation when you need a 36vdc sensor but dont have one in stock - time to get the 24-240v one out!!

 

[JohnW2]

ever since ive been in the industry its always been specified like that on everything which has a variable voltage. From relays to sensors to power supplies.

Fair enough - that's what I asked in my initial post (whether this is a conventional way they do it). As I said, it just seems a bit odd, since 'a range is a range' - so to quote a range and a "± margin" above and below that range is, in general, very unusual, and (IMO) rather odd! I have to say that, in my experience, relays, contactors, power supplies and other things which accept a range of input voltages generally just state the 'operating voltage range', without any margins over and above that range.

Kind Regards, John

 

[bhm1712]

ever since ive been in the industry its always been specified like that on everything which has a variable voltage. From relays to sensors to power supplies.

Fair enough - that's what I asked in my initial post (whether this is a conventional way they do it). As I said, it just seems a bit odd, since 'a range is a range' - so to quote a range and a "± margin" above and below that range is, in general, very unusual, and (IMO) rather odd! I have to say that, in my experience, relays, contactors, power supplies and other things which accept a range of input voltages generally just state the 'operating voltage range', without any margins over and above that range.

Kind Regards, John

Its found more often on electronic devices like solid state relays and sensors to name a couple. The traditional mechanical stuff will have a stated operating voltage as a rule of thumb....so your correct on that

 

[JohnW2]

Its found more often on electronic devices like solid state relays and sensors to name a couple.

Fair enough - thanks.

The traditional mechanical stuff will have a stated operating voltage as a rule of thumb....so your correct on that

They certainly have nominal operating voltages (e.g. 12V, 230V) - but if you look at the full spec, you'll usually find the range of operating voltages (usually with the 'must release' and 'must operate' voltages) - but without any of this "±" malarcy!

Kind Regards, John

 

[EFLImpudence]

Surely the way it is written means that it is only 'guaranteed' to work between 27.6V and 195.5V.

 

[JohnW2]

Surely the way it is written means that it is only 'guaranteed' to work between 27.6V and 195.5V.

Indeed - with one interpretation, that is what it would mean - i.e. if it is saying "the range of voltages over which it is designed to work is 24V-230V, but this range is subject to an uncertainty (e.g. manufacturing variation) of ±15%". Despite what I'm being told, I think it is very unclear and frankly ambiguous. Even with the above interpretation, since we have a range, it's not necessarily clear was "15%" means. You have interpreted it as meaning 15% of the lower figure at the bottom of the range and 15% of the the higher figure at the top of the range - but that's by no means the only possible interpretation. ... and what would 'not guaranteed to work with control voltage >195.5V mean - that it might blow up?!

I doubt that your interpretation is correct, because it doesn't make practical sense. What's would be the point, or practical usefulness, in saying that the operating range is 20.4V to 264.5V (or 24V to 230V) if it'is only guaranteed to work at voltages between 27.6V and 195.5V? It's pretty obvious that the item is designed to operate reliably with nominal 24V or 230V control voltages, so bhm1712's interpretation (i.e. guaranteed operation with 20.4-264.5V) is probably correct - no-one would buy a device which they intended to control with a nominal 230V AC supply if they were told that it was not guaranteed to work at voltages above 195.5V. However, I do not think these people would get any prizes from the 'Clear Mathematics Campaign' (if there were one!)!

Kind Regards, John