A failed frequency inverter (VFD), power supply, or safety relay can bring an entire production line to a halt — and if the manufacturer has already discontinued the series, the standard distribution channel is no longer an option. Buyers and maintenance engineers are then left with three routes: brand new surplus stock parts (known as new-old-stock, NOS for short), refurbished components, and used parts. Each of these options has its place, but they differ in risk level, warranty, and certainty of origin. We compare them fairly — with no marketing spin.
What are surplus stock parts (new-old-stock)?
New-old-stock components are brand new, never installed and never powered up. Where do they come from? Manufacturing plants and automation integrators buy more parts than they ultimately need: for projects whose scope later changed, as spares for machines that were subsequently upgraded, or as a stock buffer for the maintenance department. When a company clears out its warehouse or decommissions a line, these new, unused parts enter the secondary market — often still in their original packaging.
On the surplus market you can therefore find, for example, drives from the SINAMICS or IndraDrive families, PNOZ safety relays, programmable safety controllers such as Flexi Soft, or power supplies from the PROmax series — exactly the same products that once sat on an authorized distributor's shelf. The difference lies in the route the part took to reach the buyer, not in its technical condition.
The key distinction: new-old-stock is not the same as a refurbished or used part. These categories are often mixed up in listings, which is why it pays to know what to ask the seller.
Three categories on the secondary market — definitions with no sugar-coating
Refurbished parts
These are components that have run in a machine and were then repaired: capacitors, fans, power transistors, bearings, or contacts were replaced. The quality of refurbishment depends entirely on the workshop — from the scope of replaced components, through load testing, to the repair documentation. A proper refurbishment by a specialized service center is a fully legitimate solution; an anonymous “refurbishment” limited to cleaning the housing is a different story altogether.
Used parts
Components removed from running or scrapped machines and sold “as is”. No wear parts have been replaced, and the operating history — running hours, ambient temperature, overloads, short-circuit events — usually remains unknown. This is most often the cheapest option, but also the biggest unknown.
Surplus stock parts (NOS)
Brand new (factory new), unused parts sourced from plant and integrator surplus. Their technical condition matches that of parts from regular distribution; the only points to check are storage conditions and — for electronics with electrolytic capacitors kept in storage for very long periods — the possible need for capacitor reforming, which is worth asking the seller about before first power-up.
Comparison: surplus stock parts vs refurbished vs used
| Criterion | New from surplus (NOS) | Refurbished | Used |
|---|---|---|---|
| Certainty of origin and condition | High — the part has never been in operation; its condition can be verified against the nameplate number and photos of the specific unit | Depends on the service provider — requires repair documentation and a test report | Low — load and failure history is usually unknown |
| Warranty | Provided by the surplus seller (at RECOSTOCK: 12 months) | Depends on the refurbishing company and the scope of repair | Often none, or only the seller's statutory liability |
| Operational risk | Comparable to a part from official distribution | Moderate — depends on the quality of refurbishment | Highest — wear components are closer to end of life |
| Availability | Also covers discontinued series, as long as they circulate in surplus stock | Good for popular, high-value components (drives, spindles) | Wide but random — depends on machine teardowns |
| When to choose | Critical machines, safety systems, parts discontinued by the manufacturer | High-value components when NOS is unavailable and the service provider is credible | Non-critical machines, test rigs, limited budget |
When surplus stock parts win
In two situations, the advantage of NOS is particularly clear.
First: discontinued components. A machine's lifecycle is usually longer than the lifecycle of the electronics controlling it. The manufacturer ends support for a series and announces a successor — yet the machine still has to keep running. Replacing a drive with a newer generation often means changes to wiring, parameterization, and sometimes the supervisory software as well. A brand new (factory new) part from surplus stock, identical down to the part number (MPN), allows a true one-to-one replacement — with no modifications and no compatibility risk. This applies especially to drives and servo drives, where firmware version compatibility and matching motor parameters genuinely matter.
Second: safety system components. Safety relays and safety controllers — families such as PNOZ or Flexi Soft — are responsible for the effectiveness of a machine's safety functions. In devices with relay outputs, the switching endurance of the contacts (described by the B10d parameter) is consumed with every operation. With a used part, you never know how much of that service life is already gone; with a new part from surplus stock, the counter starts at zero. That is why, for safety circuits, it is sensible to choose brand new (factory new) components — you will find them among our safety controllers.
It is also worth adding to this list any machine whose downtime generates high costs: process bottlenecks, continuously running lines, machine tools with CNC electrospindles. There, saving money on a part with an unknown history rarely pays off.
When used or refurbished parts make sense
To be fair: you do not always have to buy new. A used part can be a rational choice when:
- the machine is not critical to production, and its downtime stops nothing beyond the machine itself;
- the component goes to a test bench or a training mock-up, or serves as a donor of subassemblies during diagnostics;
- the budget is a hard constraint and the risk of premature failure has been consciously accepted;
- a part is needed "right now" to temporarily get the machine back up and running.
Refurbishment, in turn, holds its ground for expensive components — higher-power drives, CNC electrospindles, power modules — when a new unit is no longer available anywhere, including surplus stock. The condition: a credible repair service, a documented scope of repair, and testing under load.
How to safely buy parts from surplus stock
The secondary market for automation components can be opaque, so before buying it is worth checking a few things:
- Identification by MPN. The foundation is the part number from the nameplate — it is this number, not the general series name, that determines interchangeability. At RECOSTOCK, every product is identified precisely by MPN, and the photos in the listing show the exact unit you will receive.
- An unambiguous declaration of condition. The seller should state outright: brand new (factory new) from surplus stock, refurbished, or used. If the description avoids this — ask.
- Warranty in writing. RECOSTOCK provides a 12-month warranty on brand new (factory new) parts from surplus stock, and every purchase is documented with a 23% VAT invoice — which matters both for accounting and for any potential claims.
- Logistics. When a breakdown strikes, time is what counts — at RECOSTOCK we ship orders within 24 h, by courier or to parcel lockers.
There is also the other side of this market: if your plant itself keeps unused PLC controllers, power supplies, I/O modules or pneumatics from completed projects on its shelves, RECOSTOCK offers automation surplus buyback with a quote within 48 h — just fill in the form and we arrange collection from anywhere in Poland.
Summary: match the category to the machine, not to the price
The "NOS, refurbished or used" decision should not start with the price, but with the question: what happens when this part fails? For critical machines, safety circuits and discontinued components, NOS combines certainty about the technical condition with availability that official distribution no longer provides. For secondary machines and test applications, used parts remain a sensible, cheaper alternative — with a conscious acceptance of the risk.
If you are looking for a specific part number — a controller, drive, power supply or I/O module — check the current range of brand new (factory new) surplus parts in the RECOSTOCK shop. Every item is identified by MPN, with photos of the actual unit and a 12-month warranty.
FAQ
What is the difference between a new-old-stock part and a refurbished one?
A new-old-stock part is brand new (factory new) — it has never run in a machine and comes from the surplus stock of a plant or a system integrator. A refurbished part has been in service, has failed or worn out, and has been repaired: selected subcomponents were replaced. NOS retains the full service life of all its components; in a refurbished part, only what the repair covered has been renewed.
Do surplus stock parts come with a warranty?
The warranty is provided by the surplus seller, not by the manufacturer — so its duration and terms need to be checked before purchase. At RECOSTOCK, all brand new (factory new) surplus parts are covered by a 12-month warranty, and we issue a 23% VAT invoice for every order.
Where do parts sold as surplus stock come from?
From the warehouses of manufacturing plants and automation integrators: from projects that changed scope, from maintenance department stock left over after line upgrades, and from inventory clean-ups. RECOSTOCK sources them, among other channels, through its surplus buyback with a quote within 48 h and collection from anywhere in Poland.
Can a used safety relay be installed in a safety circuit?
Formally, that is decided by the machine's risk assessment and documentation, but technically it is a bad idea: the switching life of the contacts is consumed with every operation, and with a used unit there is no way of knowing how much is left. For components such as PNOZ or Flexi Soft, it is safer to choose a brand new (factory new) unit.
