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Boiler and BMS remote monitoring over a SIM: a UK checklist

If a boiler house or BMS reports over a SIM, three things decide whether you hear about a fault: the signal, the alarm path and the age of the modem. Here is what to check, including what the 2033 plans mean for 2G and 3G.

What the SIM has to do in a boiler house or plant room

The SIM sits in a router or gateway that links the site controller to everything else. It carries alarms out, lets engineers in if you allow it, and does not have to depend on the building's own Wi-Fi. SimFalcon's UK boiler page describes connecting compatible boiler-monitoring devices, heating controllers and plant-room gateways without depending on local Wi-Fi [20]. Whether that suits a site depends on signal, the alarm path and the modem.

Signal: why the boiler house is a poor spot

SimFalcon's UK BMS page calls basements and metal plant rooms difficult radio environments, and says antenna placement and network choice can be as important as the SIM plan [19]. A 2014 report commissioned by Ofcom measured how building materials affect radio signals [9]. On a small house, foil-backed insulation plus metal-coated double glazing added 5 to 10 dB to building entry loss, and foil over the windows and doors added about 5 dB more. A boiler house is not a house, but the same physics applies. For the survey:

Getting alarms to SMS and email

SimFalcon's UK boiler page notes that some monitors use SMS or voice alerts, while others use IP data through an integrated modem or router, and that SMS alerts are available on suitable plans and compatible hardware [20]. Confirm both before ordering. For missing texts, see our SMS problems guide.

In Niagara 4, an SMS gateway maker documents the supervisor route as alarm class, then recipient, then an SMS gateway that sends the messages over the mobile network and must be reachable from the station over the network [11]. Some cellular routers also report their own events by SMS or email. Teltonika notes that email needs an email account and network connectivity, and SMS needs the active SIM [6]. Whichever route you use:

One SIM, several networks

A multi-network SIM can allow registration on more than one supported network. SimFalcon says multi-network is possible where the cellular router supports the required configuration, and that selected multi-network connectivity can help at basement or difficult-building locations [19]. It cannot fix a site where every network is weak. Sort the antenna first, using our weak or no network guide.

If the router fails over between links, check the health test. Teltonika's documentation says an interface is judged offline when none of its configured test hosts replies, and is always treated as up if none is set [7]. With an empty list, a dead link may never trigger failover.

Do you need a fixed IP address?

Not always. SimFalcon's UK BMS page says cloud-connected systems may only need outbound access, while direct engineer access can need a different network design [19]. If your supervisor or cloud platform calls out from the site, the address matters little. If an engineer must connect in, it matters a lot.

One reason is address sharing. Providers can put many subscribers behind one public IPv4 address using carrier-grade NAT, and the IETF notes this limits communication with the rest of the Internet substantially [8]. So ask your SIM supplier what a SIM is given, and whether a private APN or a VPN is the better design. SimFalcon lists private APN options on its boiler page [20]. Our APN setup guide covers the router side.

Who gets remote access, and when

A second route into a plant room is part of the building's attack surface. A 2020 blog from the UK National Cyber Security Centre on remote access to operational technology suggests considering a request process for third-party access, such as enabling and disabling an account when required or having the vendor request a time-based one-time passcode, and says guest access should be logged [18]. It also stresses multi-factor authentication and an up-to-date record of assets, and says routing communications through a VPN can help where a sensor or actuator cannot provide enough integrity or confidentiality itself [18]. It was written for critical national infrastructure, so apply it in proportion.

Older GSM kit and the 2033 plans

Mobile UK says all the mobile providers have confirmed to the UK Government that they do not plan to offer 2G and 3G beyond 2033 [2]. Its Q&A adds that each network operator has its own 2G timeline, and that some older IoT and machine-to-machine devices rely on 2G, sometimes as a back-up [3]. Mobile UK also says Virgin Media O2 announced plans to begin phasing out 2G in 2029 [2]. For businesses, it advises contacting device providers about upgrading to 4G or newer [3].

Radio in the modemWhere it standsWhat to do
2G / GSM onlyOn a timeline set by each networkNo network plans to offer 2G beyond 2033 [2], and each has its own 2G timeline [3]. Ask your network for its dates. Replace the oldest units first.
3G onlyHigher riskMobile UK says 3G is being switched off gradually, with 2G plans following afterwards, and that no network plans to offer 3G beyond 2033 [2]. Ask your network whether 3G still serves the site, then plan a 4G modem or replacement unit.
2G and 3GMay be relying on 2GMobile UK notes some older devices rely on 2G, sometimes as a back-up [3]. Test which features still work.
4G or newerThe upgrade Mobile UK advises [3]Check that the device supports the bands the network uses.

Can a pay-as-you-go SIM in an old GSM boiler alarm be replaced? SimFalcon's UK boiler page says possibly, if the device supports the required mobile technology and SIM configuration, and that older GSM equipment should be checked carefully before changing service [20]. A new SIM cannot add a radio the device lacks. Our 2G and 3G switch-off guide has a quick device check.

Also look for dial-in modems and alarm diallers that open a circuit-switched data call by dialling a GSM number. A Dutch supplier's notice on that service ending on 2G advises replacing such units with ones that support internet-based data over GPRS, 3G or 4G if data transfer is still needed [10]. That notice concerns Dutch networks, so ask your own supplier what applies on UK networks.

A checklist for FM and M&E teams

  1. Build one register of every remote link: site, controller, modem or router model, radios supported, SIM, network and what it carries.
  2. Flag 3G-only units for replacement. Then check the 2G-only ones against your network's 2G timeline and the 2033 plans.
  3. Survey signal at the antenna position, run an end-to-end alarm test, and file both results.
  4. Name the owner of each SIM contract. SimFalcon's UK pricing page says prices are per SIM per month, billed annually [21].
  5. Decide who may connect in, how they are authorised and where it is logged [18].
  6. Agree scope. SimFalcon says it supplies managed SIM connectivity and basic activation and APN guidance. Installation, wiring, programming and router setup are not included unless agreed separately [19].
  7. Estimate data use from how the site is run. Remote desktop, VPN sessions, logs and firmware updates can increase it significantly [19].

Where SimFalcon fits

SimFalcon supplies managed IoT SIMs for BMS routers, HVAC controls, energy monitoring and smart-building telemetry [19]. See the BMS SIM page, the boiler monitoring SIM page and the pricing page. SimFalcon's BMS page asks you to confirm whether the system only makes outbound cloud connections or whether engineers need to start remote sessions [19]. Send that, with the router or gateway model, through the contact page.

Sources

Frequently asked questions

Do BMS systems need a fixed IP?

Not always. A cloud-connected system may only need outbound access, while direct engineer access can need a different network design. Ask the SIM supplier how addresses are handled before you decide.

Can I swap a pay-as-you-go SIM in an old GSM boiler alarm?

Possibly. The device has to support the required mobile technology and SIM configuration, so check the model first. A new SIM cannot add a radio the device does not have.

How long will UK networks keep offering 2G and 3G?

Every mobile provider has told the Government it does not plan to offer 2G and 3G beyond 2033. Mobile UK says Virgin Media O2 announced plans to begin phasing out 2G in 2029, and that each network operator has its own 2G timeline. Ask your network for its dates.

What should I check before giving a contractor remote access to a BMS?

An NCSC blog on remote access to operational technology suggests multi-factor authentication, considering a request process so supplier access is enabled only when needed, logging guest access, and keeping an up-to-date record of assets. It says a VPN can help where a device cannot protect its own traffic. It was written for critical national infrastructure, so apply it in proportion.

Can a better antenna fix poor boiler-house signal?

It can help. Measure first, then try the antenna nearer a window or outside the building or enclosure, and keep the connectors tight. A multi-network SIM does not fix a site where every network is weak.

Questions about connectivity for your equipment? Talk to SimFalcon or ask Engineer Support.

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