Welcome! Here are the website rules, as well as some tips for using this forum.
Need to contact us? Visit https://heatinghelp.com/contact-us/.
Click here to Find a Contractor in your area.

Surge protection for Mod-Con boilers?

WillieJ Member Posts: 16
Homeowner here with a Lochinvar Whn085. Do any of the pros here include electrical surge protection on their mod-con installs or on any of their control systems? My previous boiler was a very simple 1978 vintage Weil McLain with line voltage thermostats for the B&G circulators, so no electronics to protect there.


  • SWEI
    SWEI Member Posts: 7,356
    Out here in lightning country, YES. We install point-of entry surge suppression and frequently upgrade the grounding electrode system to make sure it actually works.
    Jean-David Beyer
  • icesailor
    icesailor Member Posts: 7,265
    Here in the land of the crooks and the sun, FPL offers a lightning protection package with a guarantee that if lightning causes equipment to blow up or fail, they replace it. $9.00 per month. It is just a device that is almost the size of a Smart Meter, that plugs into the meter socket and the meter plugs in it.

    There is a lot of controversy from the cheap, paranoid class about smart meters. Some have caused fires on really old Florida services. I think it is a ploy by FPL to save their butts from bad meter sockets that make bad connections after the meter change. I seem to be the only one to have taken advantage of the offer. I consider it cheap at twice the price. That same cheap and paranoid class can't believe that a 40 year old meter socket might have bad connections and FPL just wants to steal their money. Like oil company's putting bigger nozzles in boilers so they use more fuel.

    Urban Legends galore.
  • WillieJ
    WillieJ Member Posts: 16
    I'm not in lightning country here, 85 miles north of Seattle, almost to Canada.
  • SWEI
    SWEI Member Posts: 7,356
    Surge suppressors work by diverting the energy in a surge to ground. If the building does not have a good ground, there is no point in wasting your money on a better surge suppressor. The best and shortest path ground is at the service entry, where the grounding electrode system connects to the service. The overwhelming majority of unwanted energy seen in residential and light commercial buildings comes from sources external to the building, so the best place to install surge suppression is at the main panel. Industrial and large commercial buildings frequently have internal sources of unwanted energy, primarily from large motors and other heavy loads (welders, elevators, etc.) that dictate additional surge suppression techniques, but the first place to start is at the front door, where wires from all the utilities first enter the building.

    Much of Florida has high groundwater and conductive soil, so a standard rod is easily driven and will generally provide a low impedance path to ground. Out here in the rocky west things get a whole lot more challenging. Much of western Washington also has fairly conductive soil, so a service entry protector should be a simple install.
  • BobC
    BobC Member Posts: 5,401
    I had my service redone this summer, they installed a whole house surge protector that connects to a 2 pole 50a breaker in the box.

    Nothing will protect you from a direct strike but the manufacturer of the control systems could add credible surge protection for about $5 but that would upset the corporate bean counters.

    Smith G8-3 with EZ Gas @ 90,000 BTU, Single pipe steam
    Vaporstat with a 12oz cut-out and 4oz cut-in
    3PSI gauge
  • SWEI
    SWEI Member Posts: 7,356
    Most modern power supplies already include MOVs. They are relatively small, because feeder inductance limits the available fault current at the end of a branch circuit. A nearby lightning strike will cause a very fast spike that gets time slewed as it moves towards the loads. It's the rise in ground potential that causes most of the havoc in buildings, which is why bonding and grounding are so critical to modern electronics.

    High frequency noise (which is below the clamping voltage of the MOV) must be filtered out by the input circuitry of the power supply. This is the designer's job, and some do it better than others. The Honeywell MCBA (used in many mod/con boilers during the last decade or so) was rather sensitive to line noise.
  • kcopp
    kcopp Member Posts: 4,188
    I install a 900+ joule surge suppressor on all my modcons and tankless WH. Some come w/ a plug , others I add a plug and install a grounded outlet. I did install a UPS on one unit that was having issues w/ burning out boards.
  • icesailor
    icesailor Member Posts: 7,265
    Meter Treater
    Secondary Surge Supressor
    # 400-Isl

    Search "meter treater. Residential. #400 series.

  • john p_2
    john p_2 Member Posts: 365
    Kcopp, would like to see a pic of you the surge suppressor installed on the Mods/Con if you have them
  • Jean-David Beyer
    Jean-David Beyer Member Posts: 2,666
    Here is the one I have. It fits in the service entry panel in the space occupied by a double circuit breaker. It is for a Square D QO panel. They have others for their other panels.


    You should probably look at this for more complete description:

  • kcopp
    kcopp Member Posts: 4,188
    Its really nothing all that special. I just wire in a line cord to the power to the boiler. Then plug it into an outlet. The surge suppressor is in the outlet.

  • Larry_52
    Larry_52 Member Posts: 182
    Use an isolation xfmr at the source or isolation xfmr with incorporated surge protection. If the product is built well it already does have the isolation xfmr.
  • msgale
    msgale Member Posts: 1
    I lost my control board($600) after a power blackout,(along with other electronics in my home,)
    So ,now i have a whole house surge protector at the meter plus one in each panel box, and also point of use at the boiler. And all of it ( mostly self installed) came to less than the 600. I lost on the mod-con board