Generator and ATS BMS Integration
Most standby generators are tested weekly and understood annually. We bring the generator and ATS into your BMS — run, fault, available, changeover, fuel, battery and runtime — and, where the generator specialist defines it, wire the volt-free start or enable request too. The sequencing and safety stay with the generator control panel; we provide the interface. Across London, Kent, Essex, Surrey and Sussex.
A generator that starts is not the same as a building that transfers
The weekly test is usually run off-load. The engine fires, someone signs the logsheet, and everyone assumes the building is covered. What that test does not prove is whether the transfer switch would actually change over, whether the set would carry the load once it did, or whether the starter battery has been slowly dying since the last service visit.
None of that is visible unless the signals come back to somewhere people look. The generator control panel already produces them — run, fault, available, common alarm, ATS position, fuel level, battery voltage. Our job is to get those points onto the BMS, alarmed and trended, so a flat battery is a Tuesday-morning email rather than a discovery during a power cut.
This is controls and integration work. We interface to the generator control panel, we do not maintain the engine — see the scope note below.
What We Monitor and Integrate
Exactly which points are available depends on what your generator control panel exposes. Establishing that is the first thing we do on site.
How the generator connects to the BMS
There are two routes and the generator control panel decides which one you get. The straightforward route is volt-free contacts: the panel provides dry contacts for run, fault, available and common alarm, and these wire into BMS digital inputs. It is robust, it is protocol-independent, and it is what most older sets support.
The richer route is a protocol connection where the panel supports one — commonly Modbus RTU over RS-485, sometimes BACnet. That gives you analogue values as well as states: fuel level as a percentage rather than just a low-fuel alarm, battery voltage as a number, kW output and runtime hours you can trend. Where we take that route, the usual RS-485 rules apply — 120Ω termination at both physical ends of the segment, and polarisation at one designated point. Our guide to end-of-line resistors and termination covers that in detail.
Most of what the BMS handles is status — reading run, available, fault and changeover back from the generator and ATS. Where the generator specialist defines it, the BMS can also issue a volt-free start or enable request through a permissive interface. That is a request, not control: automatic start sequencing, engine protection and every generator safety function stay with the generator control panel and its supplier. We wire and prove the interface; we do not take over the sequence. Either way the points land in the BMS the same: Trend, Distech, Siemens or any BACnet-capable head-end, with a generator graphics page, alarm routing out of hours, and trending that turns the weekly test into a record rather than a signature. Where an interface panel is needed between the generator and the BMS, we build it — see our control panel design and manufacture service.
What we do and what we don’t
Being straight about this saves everyone a wasted site visit. Alpha Controls is a BMS and controls contractor, not a generator maintenance company.
We do
- Interfacing the generator control panel to the BMS
- Status, alarm and analogue point wiring
- ATS and changeover status monitoring
- Volt-free start/enable requests and permissive interfaces, where the generator specialist defines them
- Modbus and BACnet integration
- Graphics, alarm routing and trending
- Interface and control panel build
We don’t
- Automatic start sequencing, engine protection and generator safety functions — these stay in the generator control panel
- Engine servicing or repair
- Alternator work
- Fuel system maintenance or fuel polishing
- Load-bank testing
- Supplying the generator set itself
We work alongside your generator specialist rather than replacing them — and we are happy to agree the interface scope with them directly.
Common questions
What is generator monitoring on a BMS?
Generator monitoring means bringing the standby generator's status into the building management system so its condition is visible alongside the rest of the plant. Typically that is run, fault, available and common alarm status, ATS changeover position, fuel level, battery voltage, temperatures, output and runtime hours. Where the generator specialist defines it, the BMS can also issue a volt-free start or enable request through a permissive interface. Automatic start sequencing, engine protection and generator safety functions always stay in the generator control panel — the BMS requests and watches, it does not run the start sequence.
Do you service or repair the generator itself?
No. Alpha Controls works on the controls and integration side — the interface between the generator control panel and the building management system, the wiring, the status points, the alarms and the monitoring. Engine servicing, alternator work, fuel system maintenance and load-bank testing are for your generator specialist. We work alongside them rather than replacing them.
Can you integrate a generator with a Trend or Distech BMS?
Yes. Interfacing is usually via volt-free contacts from the generator control panel into BMS digital inputs, or over a protocol where the panel supports one — commonly Modbus RTU or BACnet. Both routes map into Trend, Distech, Siemens or any BACnet-capable system. Which is appropriate depends on what the generator control panel exposes, which is the first thing we establish on site.
Can the BMS start the generator?
The BMS can issue a volt-free start or enable request to the generator or ATS system, and Alpha Controls wires that interface where the generator specialist has defined it. But a request is not control. The generator control panel retains automatic start sequencing, engine protection and every safety function — it decides whether and how the set starts in response to the request. We provide and prove the interface; we never take over the start sequence or the protection.
How do you monitor whether the weekly generator test actually worked?
A test that starts the engine is not the same as a test that proves the building would transfer. Monitoring run status alongside ATS position and on-load status shows whether the set started, whether changeover occurred, and how long it carried load. Trended over months, that turns the weekly test from a logsheet signature into evidence.
Which areas do you cover for generator monitoring?
Alpha Controls works across London, Kent, Essex, Surrey and Sussex from our base in Gravesend, Kent — including East and West Sussex, Crawley, Brighton, and Colchester and the wider Essex corridor.