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Mod Cons + Power Outage = Quick Freeze ups? .....Boilerpro

Boilerpro_5
Boilerpro_5 Member Posts: 407
I have been thinking about this lately. With Mod cons, and many other boilers with large intake and exhaust venting conected directly outside, I would think that even a rather short power outage could lead to a boiler freeze up, where the rest of the system is within the building envelope and it would take a long time for a freeze up to occur. I thinking that a standard draft induced boiler or chimney draft boiler would do a whole lot better in power outages.
What got me thinking about this is a recent Modcon install that went through a power outage, fortunately in warmer weather, on a site so windy that I can feel a strong breeze coming out of the cabinet in the boiler room. I am thinking of including a warning about this potential for future proposals. It is very likely to dampen mod con sales, but I don't like the idea of looking a customer in the face to tell them they need to replace a very expensive new boiler after a short power failure.

Boilerpro

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Comments

  • hot_rod
    hot_rod Member Posts: 21,848
    Was it a side wall vent?

    I would think those may be more prone to cold ingress conditions.

    I've noticed a draft going up the vent and intake air pipes on the installations with vents through the roof, the chimney effect from air moving across the top and warm conditions in the boiler or space it's located in, I suspect?

    Even with a small 2" PVC vent that draft is pulling some energy from the appliance.

    hr
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • UPS & Airinlet

    BP,

    I started installing Universal Power Supplies on some of our ModCons. I've been doing this because in some areas around me we have a drop in voltage that screws up the sensor readings and locks out the controls. I am sure we could size the UPS to run the boiler and boiler circ for up to an hour to keep it from freezing or many hours if just the boiler pump runs.

    If we do not energize the house relay with the UPS there would be no call for heat so the boiler will only come on if the freeze stat on the boiler has a call for heat. I think that when this happens, according to what I read, the boiler control only then brings on the boiler circ.

    wheels
  • Hvacman
    Hvacman Member Posts: 159


    If the intake and exhaust are in the same pressure zone there is only slight risk as there would be little or no movement of air through the appliance... OTOH, I had a IBN1700 freeze hard and break as the engineer specified and Lochinvar allowed a side intake/ roof exhaust. Building had power the whole time...Freeze protection scheme in the boiler controls doesn't work when the maintenance guy shuts boiler power off :-(

    If the boiler room gets close to freezing though, all bets are off.
  • Boilerpro_5
    Boilerpro_5 Member Posts: 407
    Yes, sidewall vent....

    and the cold air coming out of the cabinet was with the cover on... strong winds out here in the cornfields. Yes I have noted that the vents on vertically vented units show a negative draft under many firing conditions. I have three installed that run up about 40 feet through the old chimnies.

    Boilerpro

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  • Boilerpro_5
    Boilerpro_5 Member Posts: 407
    I like your idea...

    keeps power usage to a minimum, but protects the boiler. I'll look into it. I suppose it would work even better with a Wilo statos pump running the boiler. I use Prestiges, so the pump draw is low.

    Boilerpro

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