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What if you dont have "boost" mode on a modcon ?

Dave Carpentier
Dave Carpentier Member Posts: 604
edited May 2022 in THE MAIN WALL
Boost mode elevates the boiler setpoint by xx degrees once a heat call exists for yy minutes long. The presumption seems to be, if you're calling for heat for that long perhaps you would like a higher temperature too.
The simplified Lochinvar (the Epic) that Im likely getting doesnt have this function. Just endpoints for the odr curve, max/mins for the temp range, and a cap on the burn%.
I cant see how this is a feature worth pining for, especially on a multi-zone hydronic setup where overlapping calls can appear to be "long" to the boiler, but isnt on an individual room's perspective. In the case of using a buffer tank with the boiler's sensor in the buffer, the burner% will modulate to correct the buffer tank temperature depending on how fast it's plummeting anyway, right ?
30+ yrs in telecom outside plant.
Currently in building maintenance.


  • flat_twin
    flat_twin Member Posts: 352
    I don't use the boost feature because the ODR is closely following normal heat loss. It's OK if the thermostat goes unsatisfied for an extended period of time on a very windy day for example. The boiler will just continue making the programmed SWT. The wind will subside eventually.
  • hot_rod
    hot_rod Member Posts: 22,394
    It has some benefits and was added because installers requested it. It is useful on slab and high mass systems. Overhead door opens for a period of time, shop ambient drops, outdoor temperature consistent, as an example. IDR limits fast recoveries.

    It’s not unlike buying a car, options appeal to some, not so much to others.

    Never thought I would ever need heated seats, until I used them for a few trips. I’d be unhappy without cruise and intermittent wipers, not to mention the 8” display screen in my new truck😉
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • pedmec
    pedmec Member Posts: 994
    a boost feature is used for unoccupied or overnight reset temperatures. your setting it to turn the boiler on at a predetermined time at an increased temperature over the calculated reset temperature so when you get up in the morning or are returning to your space from not being there you have preheated the space or is pretty close to what you want for space temperature. nobody notices that the overnight or unoccupied supply temperatures were reduced.
    just an added feature for larger buildings that have multiple tenants. keeps them from bitching that its cold while saving a little money by reducing the supply temps or in case of steam the run time length for overnight.