when to use a buffer tank?

Royboy

an 80K BTU Munchkin Contender. an older house with many remodels, so no easy heatloss calcs. from gas bills I'm estimating about 60,000 BTU at design conditions (-30F). the Contender modulates down to 19K.

delivery system is baseboards split into 4 roughly equal zones. owner wants to keep the zoning as is. I'm trying to figure out whether this warrants putting a buffer tank in the system to avoid short-cycling.

thoughts? any rules-of-thumb as to when a buffer tank is desirable?

thanks - Roy

Uni R_2

Sure...

Any of the individual zones will have lower heat loads than minimum modulation level, especially in typical and much milder weather. I think that you could get good operations from a buffer tank by piping your boiler loop to the buffer tank and then supplying the zones from the buffer tank. You could pipe the expansion tank off the buffer tank and use an auto airvent on the top as your air sccop.