Advantages of programmable relays vs PLCs in building automation?

Hi there,
has anyone perhaps used programmable relays and could tell you something about their advantages, in terms of comparison with traditional controllers?
I am referring to the application in building automation.
What is the basis of their success? After all, controllers, or even configurable controllers (of the Karno Distecha type on lon or bacnet), offer many more possibilities, such as: use of analogue, triac, also relay inputs/outputs, etc...; possibility of network connection, connection to an opc server, bms, etc....
In addition, the price comparison does not at all disadvantage the controllers.
I understand that anyone can quickly learn how to program a ladder diagram - so this is an undoubted advantage of relays, but some controllers (regulators) are even simpler! And even the programmable ones, are based on graphical environments, so you don't have to be a genius in this case! In addition, the controller gives you the possibility to connect dimmers, inverters, PWM and not just on/off.

I have my doubts as to whether there is any point in delving into this subject, but I prefer to take advice.

Hello
But what does the colleague really mean. On the one hand, the title of the thread suggests a duel on the pros and cons of PLCs versus programmable relays. And on the other hand it is in the text that the colleague considers products used in HVAC against the already mentioned programmable relays. As far as I am concerned, PLCs and even freely programmable controllers for HVAC are two completely different tales. No matter how you look at it, classic PLCs (such as the Simatica series) are still a different price level (and of course functional too) than programmable relays. Somewhere in the middle there are controllers for HVAC.
The general rule of thumb is - know the many possibilities and choose a specific apparatus for the application and not think about the overall sense of the apparatus without knowing its capabilities.
As an example, use an HVAC controller for processes containing fast variable control elements (simple logic and/or) and control of a simple process/logic sequence and you will know what programmable relays are for.
kind regards
pm001

I'm not just talking about HVAC, I'm also talking about controlling lighting or roller shutters, which the karno series controllers I've given support. There is a series for HVAC and for lighting. By giving an example of configurable controllers, I wanted to give an example of a simple control. I know these are different issues - perhaps an unfortunate comparison. However, I wanted to find an area or field of application for these relays.

pm.001 wrote:

The general rule of thumb is - know the many possibilities and select the specific apparatus for the application and not think about the general sense of the apparatuses without knowing their capabilities.
pm001

Also, to be more precise, what I mean is precisely that I would like to know examples of applications for controlling such relays. I.e. has anyone used to control sprinklers or lighting for example. What is the cost, what are the networking possibilities. Or has anyone come across available drivers for building automation protocols. Can such a possible network be connected to a server. How about technical monitoring?
Since building automation controllers offer such possibilities, I would like to know whether it is sometimes worthwhile (maybe because of the price, or maybe for something else), to use relays.

Hello
Relays (even if they are programmable) already by virtue of their name fall into the category of install-and-forget hardware - not interested in what they are doing at any given time because they do what you programmed them to do. In these applications, too, they will do their job. You can, of course, find and use models with network cards, but this is already starting to be less cost-effective and more labour-intensive than using building controllers.
Personally, I have not yet come across any programmable relays with LONWorks or BacNet protocols; rather, different variants of Buses (ModBus MBus ProfiBus) generally dominate the more industrial protocols.
By the way, I know and appreciate Distech's products, but it is from HVAC that it has its pedigree on the Polish market, while application to lighting/access control and other functions defined as so-called "intelligent buildings" is a matter of recent seasons and expansion of the product range.
kind regards
pm001

MBus is more for communication with meters (e.g. gas meters). ModBus, as much as possible, is good news. Of course, I'm not counting on such a relay going over any particular protocol, like bacnet, lon or knx.

You say there are models with network cards, and I'm more concerned with connecting to a network, consisting of various controllers and to a server, so that I can see what's going on there, for example:

Relay---Transmitter---Transmitter--->BRAM<---Lon---Server OPC---KNX

Because I understand that buying a 3x relay with a network card is not worth it.

And one more question, because I haven't come across expansion modules (rather, input/output splitters) for relays. Does such a thing even exist? Because it seems that the software possibilities are not that flexible for this to be applicable. Unless for "rigid" control of, for example, a group of roller shutters.

Hello
I may be wrong but I would give my head that Chuck Norris has not yet plucked the relevant pages from the internet so I would recommend a little more invention of your own in your search
For starters, I suggest reading the material for 2 products Logo and Easy
By the way

MateuszAuto wrote:

You say there are models with network cards, and to me it's more about connecting to a network, consisting of various controllers and to a server, so that I can see what's going on there

How do you imagine connecting to any network without a suitable network card. The fact chips can be permanently mounted without replacement but IMHO they have to be
kind regards
pm001

pm.001 wrote:

Welcome
I may be wrong but I would give my head that Chuck Norris has not yet plucked the relevant pages from the internet so I would recommend a little more invention of your own in your search
To start with I suggest you look at the material for 2 products Logo and Easy
By the way
pm001

I'm not going to go all Orwell against the prevailing rules here, so I'll explain again:

Of course, I respect your opinion on the current topic and your experience in the field of building automation (at least that's my impression). However, as I've written before - I'm looking for the opinions of people who have been exposed to this and have enough knowledge of building automation controllers to say in which cases (and why), they use instead - programmable relays.

Of course, I read quite a lot about controllers before writing here. Today I know a lot more, but I make no secret of the fact that I don't delve too deeply into the subject, because I'm doing several things at the same time and need to focus on it all too. I also made it clear at the beginning that I needed some kind of incentive to get into relays, and as you can see - the willingness to learn on my part is there. Only that I don't know if I will need it.

But, once again: I'm all about practice, feedback, etc....

pm.001 wrote:

How do you imagine connecting to any network without a suitable network card. Fact chips can be permanently mounted without being replaceable but IMHO they must be
pm001

Right, no point. No communication will take place, without a communication module.

Greetings.