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Mod-Con Piping (8 Posts)
Mod-Con PipingHave any contractors found commonality between Boiler Manufactures piping Diagrams, minimum pipe size and circulator sizing on the boiler primary loops.
Like those boilers that have common heat exchangers HTP Elite, Burnham ES, Peerless Purefire etc with the Giannoni type? Sometimes we are forced to substitute one for another based on availlablity, It would be helpful for me if any one logged the requirement differences between each based on common btu output
YesThey all provide over sized boiler pumps which causes short cycling in most applications.
They should leave pump selection to the installer based on his application. They should also make the manuals more clear on what minimum flow rate means. There is too much confusion where its taken that you always need to maintain that flow rate at all times and thats just not true. As you can tell this is a subject that bothers me."The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."
a knee jerk reactiongoing back to the early '90's copper tube boiler days. When the installers sized the pumps and the majority of those HXers failed from under pumping conditions.
I see more and more the manufacturers give you a selection range for the pumps based on the delta t that the boiler can safely handle. With many choices of multiple speed pumps finding the right pump is not a problem.
Until we see the Euro type pumps with the ability to modulate from the on-board boiler control. You can find a selection of these PWM pumps now if you can deal with 230V, one leg and ground wiring :)
The ability to modulate from the on-board boiler controlis a big deal, and I remain mystified as to how this seems to have escaped notice on this side of the pond.
Circ Sizing on Hi Eff BoilersALL manufactures have listed min/max GPM/Head charts in their I&O manuals.
Currently there are two major players in the SS Modulating/Condensing market. AIC & Giannone.
The AIC (Firetube) has little head loss and lots of volume. The boiler circ requirement for this unit (up to about 250MBH) is only a 007 (nrf22, UPS1558, etc)
The Giannone is a WATER TUBE boiler. This boiler needs higher velocity to keep the passageways CLEAR from build up (like a 0011 on a 150MBH) . Because of the higher GPM plus smaller waterways you will have higher head. Ignoring the manufactures required circ on these and taking on the responsibility yourself is also accepting the warranty upon yourself. If you do not have enough flow, you will build up debris on the firing surface and you will shorten the life expectancy of the heat exchanger. See attached pic as to what is happening in your heat exchanger water ways when you have low flow.
Don't save the $$, follow the recommendations.
Circulator Sizingis indeed critical, and we all agree that proper hydraulic selection is required.
I have observed that the 'recommended' makes and models of pump are almost always too large. This raises pumping costs and lowers delta-T across the HX, which results in higher return temps and lower efficiency.
Circulator SizingMost manufactures are working VERY hard to keep their I&O manuals up to date. I know first hand that both NTI & Lochinvar provide all the information for the intelligent installing contractor to make an intelligent decision.
That said, 99% of the "trouble" jobs I go out on are due to improper installation. Almost half of these are caused by improper location/size of the circulator. The other half by improper venting.
Go figure, most of the I&O manual is spent on these two subjects. ;-)
They all provide infoand we live by the proper use of those HX flow curves.
My issue is with the specific pumps recommended for specific conditions.
Take a look a p.36 of the Lochinvar WH I&O manual. The same circulator (007 equivalent) is recommended for 10 different combinations of boiler size and ∆T. Just to make it interesting, they've assumed different hydraulic conditions with each of the three ∆T conditions. While the individual numbers are likely accurate, they don't actually make much sense in the real world. One example: in order to get the 055 working at full efficiency into a short primary loop, I need a pump which will move 3 GPM into 0.5 ft or less of head. Those aren't exactly common, but putting a 007 there is just silly -- unless you're direct pumping the boiler into a system whose curve plays nice with a 007.