BadgerBoilerMN
Hydronic Heating Designer
===============================
MY RESPONSE: something quite different is indicated in viessmann document. And this difference is that P/S does promote condensing in condensing boilers
and this is what i wrote in my post:
These are clear guidelines for LLH
also make a note that in viessmann opinion primary secondary arrangement does promote condensing in condensing boilers, quite different from your statement.
Again, the difference is that BadgerBoilerMN stated primary secondary is not progress where condensing boilers are concerned, and viessmann statement is that primary secondary does promote condensing in condensing boilers. you see, this is the difference
MY RESPONSE: P/S does promote condensing in condensing boilers according viessmann manual
Also if you read viessmann list of benefits, you see there are benefits in P/S, and this is quite different from the statement:
QUOTE: There is no logical argument for doubling electrical operated costs and the chance of a nuisance no-heat by adding a redundant circulator to any single zone hydronic system. END OF QUOTE
it is not just redundant pump and doubling electrical costs.
please read list of benefits.
Also Dan Hologan wrote a book, named " primary secondary pumping made easy", addressing all these benefits, you can see picture of its cover few posts earlier, read it, you might like it.
I have a signed copy, thank you. Fortunately I have actually installed, distributed and manufactured condensing boilers for a living since the 80's. I agree that it is best for the average plumber to use P/S, one cannot argue this point. I am speaking mainly of single zone conversions in which the flow rate thought distribution is greatly enhanced in the case of a gravity system (any flow would be an improvement) and the flow through the low-mass condensing boiler (many will suffer a 45° delta-T) is easily satisfied with the smallest of common circulators. Adding a extra pump in such a case would be wasteful and ignorant neither of which I care to be associated with. Thus we do not use Buderus, Weil McLain Ultra, SlantFin condensing for small hydronic systems where P/S can't be rationally justified, as they share your the single-minded opinion, with one intellectual advantage; in benefits them in fewer service tech calls and they don't pay for the considerable installation and operating cost of the redundant pump.
Simply put, if the flow through the system and the boiler are adequate to both no advantage can be gained by applying P/S piping either for hydraulic separation or flow control. The design has it's applications, mostly commercial, multi-boiler and multi-temperature applications but a steam or gravity conversion most certainly is not one of them.