Turndown Ratio Question

Cyclist77

As a combi boiler has the turndown ratio is an oversized unit as much of a concern as a ci boiler?

Jamie Hall

No — but you still want to get close…

mattmia2

It becomes much more important if there is zoning involved. The more oversized it is, the greater chance that the lowest trundown ratio will be more output than the smallest zone can dissipate. The mass of a cast iron boiler can buffer somewhat. The low mass of a mod con is going to short cycle without some sort of short cycle logic on a zone that is smaller than its lowest turndown ratio.

hot_rod

If it is a combi boiler the turndown can be more important as you size to larger load. The DHW is often the larger load.