Help me pick a circulator (indirect water heater)?

John@Reliable_13

006B is a standard pump for coil and booster tank set-up like you have. Depending where pump is add ball valves on either side for service, if above tank really not needed.

Charles_8

Too many choices...

What size circulator pump should I use for my proposed indirect water heater system? Burnham V-75 steam boiler with a V1-2 3.25 gpm tankless coil, 40 gal. storage tank.

There is a bewildering array of pump prices, size and brands, but most look far too large for this application. Don't I only need 1 or 2 gpm at 5 or 10 ft. water head (around 3-5 psi drop in the coil)?

Also, what diameter should the lines be from the coil to the pump and tank? Is 1/2" or 3/4" copper adequate?

thanks

-Charles

kevin coppinger_4

a Taco 006B...

B for bronze will be fine. It has 3/4" sweat ends. Make sure it is piped properly. Most coils are 1/2 " that will work.

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Steamhead (in transit)

If you're circulating water thru the coil

the 006B should be fine. If not, I'd use a bronze B&G 100 or Taco 110 or similar 3-piece unit. The water characteristics in a steam boiler can shorten the life of a wet-rotor unit like the 006B. The mechanical seal in a 3-piece circ keeps this nasty water away from the circ's working parts.

If the indirect manufacturer says 3/4-inch pipe is OK, that's all the recommendation you need. 1/2-inch sounds too small to me, but go with the manufacturer's specs and you should be fine.

If you're pumping thru the coil, install the circ so it pumps away from the tank toward the coil. If pumping boiler water, install the circ so it pumps away from the boiler, toward the indirect. These placements will prevent cavitation.

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Charles_8

Ordered the Taco. thanks!

I just ordered a Taco 006B (bronze) with 3/4" threaded connections. There was quite a spread of prices, over 60% difference, so a few minutes online searching was time well spent!

I'll be pumping hot water(not boiler water) through the tankless coil back to the storage tank. Since there is a significant pressure drop in the coil, I definitely plan to have the pump push through it rather than suck (as you point out, it could cavitate. Centrifugal pumps are much better at pushing than pulling anyway). Also the water will be cooler on that side of the coil.

Thanks for the tips, everyone.
-Charles