Screened cable

[ban-all-sheds]

The pic was to give you a clue as to the type of enclosures used in most domestic and light commercial properties

The the clue tells us that the wrong type of enclosures are being used in most domestic and light commercial properties.

and that metal Din rail boxes are seldom required.

Well I didn't say they should be metal, but DIN rail absolutely. "Seldom required"? The installation in your photo really is crying out for one - it really isn't up to professional standards.

Has anybody here got a photo of something closer to how that should have been done?

It was a test rig I did as a 'sparky' for a customer friend using the items I had in my van.

So how was it done in "production"?

Not sure what 20th century legacy means or what it has to do with OT,

What it has to do with OT is that they decided to make OT work over 50+ year-old traditional domestic wiring systems, rather than saying "we are entering a new world of intelligent networked controls and appliances and we will build an infrastructure appropriate to that".

There is nothing " hopelessly crippled by the 20th century legacy" in the installs I provide?

It seems to be intrinsic to OT, so yes, there is.

I will look into Cat 5 type cables but none of the kit I use ( apart from Rhiani sequencing software) has this option.

Dear God.

 

[ban-all-sheds]

I was not trying to enter a dick swinging competition.

Nor am I, honestly.

But I truly think you have no idea how you should be doing this, nor how much you should be raising your game.

 

[ecowarrior]

Thanks for all your sarcastic comments and the total lack of constructive input. It must be great being Mr perfect. all you ever do is show off how fantastic you are & how crap everyone else is. My wife spends her life itching for a fight - you would spar well with her. You have managed to twist everything into something its not so u can criticise. The one off test rig assembled for a friends experiment has nothing to do with heating and 'production' if there ever was any is irrelevant but well done for twisting that into something to jeer at. 99% domestic wiring centres are small IP rated enclosures of some sort and the pic was to show the in-practicability of large long glands on small enclosures, but well done for deliberately missing the point to jeer on. The OT & supporting infrastructure available to day is a light year away from how it was or may have been done 50 years ago. Shows how little you know of the subject. As to cat 5 - never used it know little about it possibly why I asked on here to get some help but again turned into a sarcastic jeer. You really must be a nice bloke with nothing helpful or positive to ever say. I assume u r on here criticising away as u r banned from closed forums where similar minded people try to help & educate each other.

 

[SUNRAY]

Thanks for all your sarcastic comments and the total lack of constructive input. It must be great being Mr perfect. all you ever do is show off how fantastic you are & how crap everyone else is. My wife spends her life itching for a fight - you would spar well with her. You have managed to twist everything into something its not so u can criticise. The one off test rig assembled for a friends experiment has nothing to do with heating and 'production' if there ever was any is irrelevant but well done for twisting that into something to jeer at. 99% domestic wiring centres are small IP rated enclosures of some sort and the pic was to show the in-practicability of large long glands on small enclosures, but well done for deliberately missing the point to jeer on. The OT & supporting infrastructure available to day is a light year away from how it was or may have been done 50 years ago. Shows how little you know of the subject. As to cat 5 - never used it know little about it possibly why I asked on here to get some help but again turned into a sarcastic jeer. You really must be a nice bloke with nothing helpful or positive to ever say. I assume u r on here criticising away as u r banned from closed forums where similar minded people try to help & educate each other.

Hi Warrior.
I think you are missing the point here completely.
As much as I hate to admit it, on this occasion BAS has it absolutely right.
No one is perfect, we all make mistakes and we all work to different ideals and if it's any consolation I have had to sort out far worse installations than yours. My reputation in the controls industry has built up by correcting bad installation like yours to the point where I am OFFERED a higher daily rate than many others ask for to get me on a job.
That really is a horrible mess especially for a brand new installation, 6 junction boxes where one will do the job-WHY? and don't answer with 'what I had on the van' that is lame to say the least. If this is the sort of work you do on a regular basis and you work from the van then the van stock should reflect this.
It will be a lot easier and tidier to do all of that in one box and quicker.
I don't see the point of taking a cable into a junction box then straight into another junction box and it looks like you have done that at least 3 times.
Loads of joins in different boxes makes it harder to wire and even harder to fault find.
I suspect that that mess you have created is adding to your interference problem.

It is important to have things secured when there are moving parts.
In future get a proper metal, yes metal, box. Make sure it is properly earthed. Make sure the terminals are secured, and not floating around. Proper terminals on DIN rail is far superior. Use 'earth' terminals for the screens. Yes I know it costs more but your reputation and quality of workmanship and reliability and... will improve dramatically when it's done properly.
I could go on but that's enough to give you an idea where to make a start.

Try and have a look in a 'proper plant room' at the way things are done, I'm not trying to say you need to adopt ALL of those same standards in a domestic or small commercial situation but you should at least take notes and work from there.

Rant over

 

[ecowarrior]

well thanks for a constructive reply. Things get out of hand with irrelevancies so quick. The picture (it appears I foolishly posted) is nothing to do with anything other than the type of boxes used in my end of heating. The point was to show the scale of box to those offering very large & long metal glands. This (pictured) job was for a mate of mine who was trying to get hydrogen from water without electricity ( apart from the motor). It was as I said wanged together with what I had in the van. It was not a paid job there was no production of it and probably before it was changed for another attempt was seen by about 4 people (even as a friend I had to sign a NDA) There was no need for anything else. It was for about a month before the jig changed yet again. It has nothing to do with my original Q. I dont need advice on Din rail boxes and plant room layouts what ever you may think. I have for the first time needed to square away earth braid from screened cable. Pardon me for having never used it before - and I was simply seeking to see if there was a magic way of doing this a neater way than I am at the moment. We have got down in needless abuse politics & god knows how much sarcasm all taken from a pic that clearly stated it was nothing to do with heating. Not that its in any way relevent - each one of those JB's was for a reason to make life simple for testing. there was a megga Data logger all in the mix there somewhere. 95% domestic heating (as by the sounds of it you know) even with cascaded boilers need little more than a large 10 way box or larger IP box with or without Din rails. In domestic I use IP plastic boxes with plastic glands. Actually on the few bigger commercial installs with maybe 4 boilers cascading I still use IP rated boxes sometimes Marina boxes so u can see whats going on relay wise inside. so - please - just to recap this was about a clever ( if there was one) way to neaten up screened earth terminals. However I thank you for your advice.

 

[ban-all-sheds]

Thanks for all your sarcastic comments and the total lack of constructive input.

So suggesting that this sort of thing:

would be better than this sort of thing:

was not a constructive suggestion?

You have managed to twist everything into something its not so u can criticise.

I've twisted nothing.

The one off test rig assembled for a friends experiment has nothing to do with heating

The context of what it's controlling is irrelevant to the wiring methods used.

and 'production' if there ever was any is irrelevant

I accepted that what you showed was a test rig, I did not know that it was not subsequently put into use. And you were the one who said it showed "the type of enclosures used in most domestic and light commercial properties", so if you were excusing its scruffiness because it was an experimental test rig, and I did not know that the system wasn't put into permanent use, it's quite reasonable to ask how you did it when the test was over and it was done "for real".

but well done for twisting that into something to jeer at.

I've twisted nothing and jeered at nothing.

99% domestic wiring centres are small IP rated enclosures of some sort

I'm sure they are. But if the scale and complexity of the wiring needed nowadays has reached the level shown in your photo then those types of enclosures are no longer fit for purpose.

Unlike the way that OT was designed to work on mid-20th century installation wiring because that's what was already there, you do have a choice about the types of enclosures and connectors you use. You don't have to carry on using lots of little boxes and choc-block just because that's the way it's been done for the last 50 years. Nor should you.

and the pic was to show the in-practicability of large long glands on small enclosures,

These are no larger than the glands in your photo:

but well done for deliberately missing the point to jeer on.

I've not deliberately missed, or jeered at, anything.

The OT & supporting infrastructure available to day is a light year away from how it was or may have been done 50 years ago.

OpenTherm ... had to run, like the existing controllers, over the existing two wires, not polarity sensitive, without the use of batteries.​

That's what I mean about locking it into a decades-old infrastructure type.

As to cat 5 - never used it know little about it possibly why I asked on here to get some help

I was the first person to suggest the use of that type of cable. It is widely available and cheap, it needs no special glands or expensive tooling, and is purpose designed to carry data signals over long distances at high rates and be intrinsically resistant to interference.

But apparently that was not a constructive suggestion.

but again turned into a sarcastic jeer.

Saying "Dear God" to the news that Cat5 cabling is not, or is very rarely, supported is neither sarcasm nor jeering.

 

[bernardgreen]

Back on topic

A good description of the OpenTherm communication system is to be found by clicking on here

This section is relevent to the discussion about interference. The original method ( before it was adopted by OpenTherm) was polarity critical but OpenTherm has modified it to make polarity non critical by adding bridge rectifier at the cable interface.

,

The only advantage ( unless someone knows better ) is that wiring errors by careless installers will not prevent the system working ( or damage components ).
The major dis-advantage is that the diode bridge will significantly decrease the receiver's tolerance of interference. Decoupling capacitors across the diodes would restore some of that lost immunity to interference.

 

[flameport]

just to recap this was about a clever ( if there was one) way to neaten up screened earth terminals.

The answer is to use the correct glands for the cable, whether that is CY or any other type.

However there is absolutely no point in using screened cables if all of the connections are in plastic boxes.

Given the very low data rate of OpenTherm (1000 bits/second), there should be no need for screened cables anyway.

 

[bernardgreen]

Given the very low data rate of OpenTherm (1000 bits/second), there should be no need for screened cables anyway.

The data rate is irrelevent as OpenTherm uses a self clocking code format. The clock that the receiver needs to receive and decode the data is embedded in the transmitted data unlike RS 232 where the receiver has to generate a clock with a frequency the same (+/- 5%) as the clock in the transmitter.

With RS232 a glitch in the data will not corrupt the data unless the glitch occurs when the receiver is sampling the received data bit.

With self clocking data formats a glitch at any time will create a false clock pulse and corrupt the data bit during which the glitch occurs.

Self clocking codes remove the need for the receiver to generate an accurate clock ( expensive when self clocking codes were developed ) and also enable a receiver to receive data at different and variable clock rates.

 

[JohnW2]

The data rate is irrelevent as OpenTherm uses a self clocking code format.

I suspect that flameport's point was that the data rate is so low that everything of a significant frequency (including the majority of potential 'interference') could be, and hopefully is, filtered out in the equipment.

Kind Regards, John

 

[SUNRAY]

well thanks for a constructive reply. Things get out of hand with irrelevancies so quick. The picture (it appears I foolishly posted) is nothing to do with anything other than the type of boxes used in my end of heating. The point was to show the scale of box to those offering very large & long metal glands. This (pictured) job was for a mate of mine who was trying to get hydrogen from water without electricity ( apart from the motor). It was as I said wanged together with what I had in the van. It was not a paid job there was no production of it and probably before it was changed for another attempt was seen by about 4 people (even as a friend I had to sign a NDA) There was no need for anything else. It was for about a month before the jig changed yet again. It has nothing to do with my original Q. I dont need advice on Din rail boxes and plant room layouts what ever you may think. I have for the first time needed to square away earth braid from screened cable. Pardon me for having never used it before - and I was simply seeking to see if there was a magic way of doing this a neater way than I am at the moment. We have got down in needless abuse politics & god knows how much sarcasm all taken from a pic that clearly stated it was nothing to do with heating. Not that its in any way relevent - each one of those JB's was for a reason to make life simple for testing. there was a megga Data logger all in the mix there somewhere. 95% domestic heating (as by the sounds of it you know) even with cascaded boilers need little more than a large 10 way box or larger IP box with or without Din rails. In domestic I use IP plastic boxes with plastic glands. Actually on the few bigger commercial installs with maybe 4 boilers cascading I still use IP rated boxes sometimes Marina boxes so u can see whats going on relay wise inside. so - please - just to recap this was about a clever ( if there was one) way to neaten up screened earth terminals. However I thank you for your advice.

As I wrote earlier -Rant over. Everything in the reply I stand by and reiterate that putting it nicely in one box is easier and far better for access for testing in R&D situations.
So back to OP- the screened cable used in the majority of my work is FST (eg Beldon 9501) style and the typical method of terminating the screen is to remove the exposed foil screen, sleeve the drain wire, fit ferules then.cover the end of sheath with hellermen sleeve or heatshrink (depending on job spec), then terminate in earth terminal. Something similar is likely with with SY style cables too due to the sheer numbers of cables involved sometimes and trying to fit that many glands can be too prohibitive as several hundred cables is not uncommon.
If just a few SY cables are involved I may use proper glands depending on situation (experience has sbown not to if there is much flexing).