Short cycling, then what?

WaterHeaterGuy

Due to the fact they are generally low mass. Superheating and flashing to steam are real concerns, not to mention that the cycling is occuring on potentially more expensive componants.

In your scenerio you said twice the boiler size as it should be... if it was a lesser percentage then potentially the unit could modulate down to an area where it could stay running, but not double.

Gene Davis_3

What problems might result in the use of a boiler with twice the capacity as your heat loss at design temp?

ALH_4

Oversizing

It depends on the boiler, but generally oversizing the boiler will hurt efficiency somewhat and prematurely wear components. Also, it means you paid for twice the boiler you needed.

With mod/cons the penalty appears to be less than with conventional boilers, possibly because of the more tightly controlled sealed combustion in a mod/con.

Gene Davis_3

Heat loss is in the low 40K range on design day. I recommended a Munchkin, either the Contender or the T50M, but my friend bought the Trinity with 100 rating, the smallest that Trinity makes. The Trinity cost was just a few shekels more than the Munchkins.

What can happen?

Unknown

Minimum modulation is what matters with modulating boilers.

the trinity's is very close to the munchkin's. Not that much difference between the two.

If there are more than a few zones splitting that load up, and no syncronization, you might consider a small buffer tank.

John Cockerill

oversizing

try lowering the high limit on the aquastat. Increases circulation and makes the house comfy

www.Exqheat.com

Unknown

that doesn't change BTU output John, and so does not help with short cycling problems. If anything, it would make it worse.