Adding function to outdoor reset

jmatthewwest

Is it possible to use outdoor reset to manage the number of zones activated during periods of warmer weather? I ask the question because I'm installing a boiler with minimum 18,000 btu/h rating, and I want to understand whether I risk short-cycling if zones are close to that heat requirement only at outdoor design temp. Is it possible to control the number of zones calling for heat when it's 30 degrees warmer outside to ensure that the 18,000 btu/h minimum is being met? Or is it preferable to allow the boiler to short-cycle rather than heating an extra bedroom when it's not necessary to do so? At some point there'll be a point of diminishing returns, I realize. I'm just curious as to your thoughts on the matter. Alternatively I can reduce the number of zones, but I'd certainly prefer to have as much zone flexibility as possible without being ridiculous about it.

EdTheHeaterMan

Overthinking

Zman

Increasing the on/off delta, adding a buffer tank and combining zones are all ways to reduce short cycling. What kind of cycles are you seeing?

STEVEusaPA

Wouldn't they all need the same btu ratio as the temperature drops, meaning those other zones are going to need some heat.
Maybe you can combine zones and control flow to the smaller zones.

jmatthewwest

System is in design now. I'm trying to incorporate more zones into the design, but some of them are at the minimum inputs of the selected boiler... seems likely on warmer days when heat is called for, (outdoor reset present) there'll be a short-cycling issue. I'm wondering if there's a way to have the controls automatically activate enough zones (even if the tstat isn't calling for heat) to prevent short-cycling as much as possible. For sure it's possible I'm overthinking it... just looking to tap the group knowledge/conjecture on the topic. Thanks, All.

JohnNY

So you'd rather heat zones that aren't calling for heat than have the boiler run a shorter cycle? Why not just use a smaller boiler since you're still in design phase, or use multiple boilers?