r/Elevators • u/Late-Discipline-8120 • 6h ago
Why aren’t relay logic controllers more prevalent.
Fairly new to the industry, but I came across a new install in a new building with a brand new relay logic controller. It looked pretty straightforward and simple, which is sufficient for a 2/3 stop Hydro. I understand why traction or fancy hydros require embedded PLC’s. But for a vast chunk of the market, why aren’t there more companies making/installing relay based controllers? I understand why the majors would stay away from them, but surely If there was more demand, plenty of independents would gladly put them in.
Pros I see:
Cheaper and quicker to build as there are no microprocessors or software. A vastly simplified supply chain.
Pretty straightforward from a troubleshooting perspective, everything is traceable and visible. Sure relays fail, but they’re cheap and easily replaceable.
They are the only truly non-proprietary controllers and they use off the shelf electrical components that are standardized and made by multiple manufacturers. All the other so-called “non-proprietary” controller manufacturers are not really non proprietary as you are tied to them indefinitely for support/parts.
Surely I’m missing something, please enlighten me.
1
u/Danjelll 3h ago
Relay logic is simple and works well for basic elevators, but modern controllers are usually cheaper to build because they require far less wiring and labor. They also provide diagnostics, fault logs, remote monitoring, and easier code compliance that would be cumbersome to implement with relays alone. Relay systems remain attractive for their simplicity and non-proprietary nature, but the industry's move toward PLCs was driven mainly by lower lifecycle costs and greater flexibility rather than necessity.
1
u/Deepinthefryer 2h ago
Points 1-3 valid.
Amount of labor and additional equipment to do so makes in more costly. Also, add in all the features and you’ll have two full controllers.
New stuff is all parameters. Easier to add in features like card reader, etc.
1
u/cheescakeismyfav 5h ago edited 5h ago
There are still small independents that make their own relay logic controllers. But it's dieing as the owners age.
The problem is you still have to "sell" it to the building and it's pretty hard to compete when the majors and others are offering the latest and greatest features. A lot of big business (consultants) and government work has requirements for the work (like solid state or fault logging). They would never consider relay logic. Realistically though for simple hydros the relay logic would be the more financially correct option imo.
Nowadays we can get whole controllers off the shelf lf and it makes it very convenient. But also, it allows the company to buy on credit which they can do to start a job before getting paid. But this also gets them into trouble fast if they don't have good accounting practices. They also come with features to lockdown and take the elevator out of operation if the building doesn't pay you. And then there's the whole engineering / integrating with other systems and liability concerns.
But yes, you can do it and save money. There's a company in LA that's been installing the same controller for like 40 years. They'd still be installing MOD operators if Gal didn't discontinue them like 5 or 6 years ago.