non-wet rotor circulators in small/efficient sizes?

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.
Status
Not open for further replies.

pybyr

Minister of Fire
Jun 3, 2008
2,300
Adamant, VT 05640
Hello all-

in another thread, Kabbott raised the fascinating idea of putting a plate HX directly in the primary loop of a primary/secondary system (the HX will be my interface between the unpressurized storage tank and the boiler and heat loads) rather than having the HX “hanging off” a secondary; his approach, as he noted, would allow deletion of one circulator.

https://www.hearth.com/econtent/index.php/forums/viewthread/21028/

On the un-pressurized side of the HX, between the HX and the thermal storage tank, I am planning to use "back to back" circulators in opposite directions as has been pioneered by folks here and is being deployed by WoodNotOil.

One factor that putting the HX in the primary may introduce is that my unpressurized loop between the HX and storage may be much more likely to siphon itself out, and/ or leave air in the circulators on the unpressurized side of things, which I know will spell trouble, fast, for wet-rotor circs.

I know that the old-type circulators had separate motors, without wet rotors, but they were huge and electrically inefficient

anyone know whether there are any current-technology, electrically-efficient, not too huge circulators that can prime themselves and that do not require being internally immersed in fluid 100% of the time?

or, for that matter, I welcome any other suggestions on how it might be possible to avoid the unpressurized side siphoning dry and pulling air into the circulators

I thought of zone valves, but from all I've read here and elsewhere, they apparently usually have small inside ports and introduce a lot of flow resistance, which I would like to avoid

thanks

Trevor
 
No, a circulator is not designed to be self priming. Most will have a pressure number listed by the manufacturer.

Grundfos UP series wants 1.3 psi or 3 ft. at 140F and 4 psi or 9 ft. at 190F

NPSH net positive suction head is a calculation that take into account pressure and the type of fluid.

This is one of the reasons un-pressurized OWF go through circs. especially when they use high head circs :)

hr
 
Status
Not open for further replies.