Hey all,

Thanks for the help y'all have provided already!  We're filing our taxes and getting set to pull the trigger on our boiler replacement.  The old one is out of the utility room & ready to be salvaged.

I spoke to our plumbing shop yesterday and he put together a package quote for us.  He mentioned something in our conversation, however, that I thought I'd run by the experts here:  He said these boilers need to be installed with TWO circulating pumps:  one upstream of the boiler and one downstream.  He didn't explain his reasoning very well.  Does this sound right or is he trying to sell me two grundfos 3 speed pumps instead of one?

System details:  1000 sq. ft. slab-on-grade with cast-iron pipes (size unk.), 50kbtu munchkin contender mod-con boiler replacing a kaput raypak.

Thanks again!
charlie

He is probably describing a primary/secondary piping design. This is common practice and advocated by all US manufacturers (assemblers to be more exact). The vast majority of my Contenders do fine with one circulator if the near piping is properly designed.

It is rarely necessary for the smaller ModCon boilers to require more than one circulator, but anticipating that most contractors will not do the math, the safe thing is for the manufacturer to recommend (or require in the case of Buderus) one circulator for the boiler and another for the system.

I personally resent operating an extra pump and doubling the chance of a boiler shut down for lack of circulation, but my customers and I seem to be alone in this concern.

Morgan is 100% spot on here. Your particular situation is very unlikely to require more than one pump.

good to hear. I was a bit skeptical. Easier to wire one pump than two as well, I'd assume. So my one pump should be installed on the return/boiler-in side?

charlie