Taco

Bruce M

Taco Tecnical Document TD10 titled Selecting Circulators mentions equivalent length of the piping circuit. It states:
"The total equivalent length of the piping circuit is the length of all straight tube segments plus the equivalent lengths of other components such as fittings and valves." That part is easy to understand but I need to know if the total length is from boiler outlet to inlet and does it include the circulator? Does a circulator have an equivalent length?

Mike T., Swampeast MO

Forget about the circulator itself, but you must include everything else* in the circuit. Piping, fittings, boiler, emitters, etc.

Pressure drop of boilers varies greatly with the design from inconsequential (old cast iron boilers) to moderate (copper tube boilers) to high (many mod-cons). Pressure drop of emitters varies as well. Old iron rads can be considered as having zero. Fin baseboard is the same as a tube of the same diameter. For iron baseboard and modern panel rads you should consult manufacturer's literature.

*Note that you include EVERYTHING in the circuit ONLY for a one-pipe loop. If a two-pipe system you compute only those elements in the most restrictive path (usually to, through and from the farthest emitter) but NOT including the branch piping/emitters of the remaining branches.

ALH_4

circulator

You are correct that there is head loss in the pump body. However, the circulator is not counted in the head loss because the pump curve reflects those losses from when they rated the circulator. Anything beyond the gaskets should be counted. As Mike stated before, use the worst-case loop for your calculations. Hopefully the loops are relatively closely matched. Siggy's HDS program spits all this information out automatically.