BBHW - Circulators

Greg Kettmann

I posted the other day and it was suggested I use the SlantFin heat loss calculator for my addition. I did this. I learned a couple of things.

First, the original plumber didn't use anything even vaguely resembling this tool. It was not possible to get the tool to come up with anything close to what's currently installed.

Second, my 18x24 sun room is going to take a lot of BTU's (say 20,000). This seems high to me, but it clearly states one thing. It won't be possible to "size" the heat for that room with any hope of keeping it "balanced" with the rest of the first floor.

The answer is simple. Make the sunroom it's own zone. That solves two problems. One, adding 20,000 BTU's would have dropped the loop temperature far more than 20 degrees, and two it's own thermostat means I don't have to be as careful about "balancing" that room with the rest of the first floor.

The problem is this. I have a Crown Aruba 150,000 boiler with a single Taco 007-3 circulator. It currently feeds four zones, upstairs, downstairs, hot water and a small one in the finished basement. There's no way the circulator can supply a fifth zone, assuming all five were picked at once. For that matter the transformer isn't rated for picking 5 zones either.

Am I correct to assume another zone is the best way to go? Assuming so, am I also correct that I'd need a second circulator and then break the existing zones "in half"? Based on what I've read that also means I need check valves, correct? Are there any issues or problems with adding a second (or perhaps a larger) transformer?

I'm not looking for detailed answers here, just a quick sanity check. I'm probably planning on a fifth zone (w/2 Taco's, check valves and larger/second transformer) with about 23 feet of slant fin radiator for the sun room (lots of windows). That's a little short from what's recommended but I'll use the high output slant fin and the 23 feet will be far more aesthetically pleasing than wrapping around a corner. The 20,000 BTU heat loss assumes zero degrees outside and we rarely get colder than that. 15-20 is a far more common "cold" night.

Thanks for any help.

JeffD_2

Don't size by your coldest temp. Size by the average low temperature. You are correct in assuming that you will need an additional pump for the 5th zone.

Joe Brix

Was one of those zones an indirect?

If so, I'd put the indirect on a circulator by itself. Maybe the indirect has a line voltage aquastat or just get a Taco switching relay to on/off the circulator. Put the new zone on the old zone valve.