Efficient circulators and switching relays

Albany Chris

I am getting ready to install a single radiant loop in my own house to keep my wife's feet warm in the bathroom. I installed a taco switching relay and was getting ready to install a bronze 006, when I noticed that the transformer in the switching relay was pretty darn warm. I stopped the install and did some research. THe switching relay is 20va, which with my shaky math comes to .18amp, which is 20W. THe pump is .6amp, and will run a lot to keep the floor toasty.

I am really annoyed that the relay, which runs 24/7/365 draws so much. It works out to about $24/yr based on my (shaky) math. And I wonder if there is a better circ to be using. It is a single 1/2" pex loop about 130ft long. I think the 003 might be enough, but have also read about the ECM ones which are much more efficient. Maybe my supply house doesn't know enough about these? Maybe I am overthinking all this and I shouldn't put so much effort into avoiding $40/ year in electric costs to run my little loop?

What are your thoughts or suggestions?

Charlie from wmass

why a bronze pump?

If you are concerned with the cost of the electricity why use a bronze pump? Wilo offers smaller pumps that may work just fine.

Charlie from wmass

If you have multiple zones

then use a multi zone relay, that would be one transformer for up to 6 zones instead of one per zone.

Albany Chris

Open Loop & One Zone

Hi Charlie, thanks for your response. It is a single zone system, open loop, run off my Vertex 100. The programmable thermostat will cycle the water in the summer. Under $650 with plates, pex, fittings and pump since the highly efficient Vertex was already there. THerefore the bronze pump.



I am certainly interested in alternative pumps in Bronze or Stainless though. I think my guy at the supply house just grabbed what he knew and commented that we would have to throttle the 006 way down...

Joe Mattiello

006 and relay combination

I had one of our electronic engineers hook up a SR501 controller in the lab to see what the actual load is.  What we learned is it draws ~120 mA (.12 amp) when running. This works out with a 120 VAC line voltage to approximately 15 VA.  Charlie who commented is correct, when he says that running a multi zone panel would be more efficient than a single zone switching relay which is the least efficient setup.  Apparently transformers use a certain amount of power just being plugged in. that’s called transformer losses. So running a relay at .12 amps, with a 006 pump at .52 amps is a total load of.64 amps or 76.8 watts.  Wow that keeps the wife’s feet warm in the bathroom at the cost of running a 75 watt light bulb.  Not bad!!  You might consider changing from an incandescent light bulb in the bathroom to a more efficient florescent light bulb.  That would be a wash so to speak...