Circulator too small?

ChrisF80

Hi, I have had a new hot water boiler installed last year. It's a Buderus G115 WS5 with a riello burner. I have 5 zones, 4 heating, and 1 for an indirect. All zones have separate circulators, all of which are taco 007. There was no temperature gauge installed on the return, so I took it upon myself to install one after reading on this site how important that information is. Since then I have noticed what I think is an issue on one of the heating zones. This particular zone is installed in an addition that was built about 10 years ago, long before I owned the house. It's a 3/4 copper series loop with about 50 feet of baseboard and I believe the total length is about 200 feet. I was watching the temperature gauges with this zone running on its own and I noticed it takes about 5 minutes for the return water just to get warm, about 110 degrees. At that time the boiler hits the high limit (180) and the burner shuts down. The supply temperature gradually drops enough to kick the burner back on(20 degree diff). The return water then goes up to about 150 and the supply continues to drop to about the same temperature and stays there for about one minute and then the thermostat is satisfied and everything shuts off. The low return temperature is making me nervous. I'm thinking the taco 007 is too small, too much head ? All other zones take about 3 minutes to get return temps above 140 and then maintain a 15 degree Delta T. Any advice is greatly appreciated, and happy holidays.

ChrisF80

I use 180 supply water because the zone for the main floor of my home (not the zone I previously asked about) is under radiated. I removed a partition wall that had a convector in it. With the remaining 2 convectors the main floor takes almost 2 house to raise 2 degrees. The boiler repeatedly hits high limit during that time. With lower supply temp that zone would take forever to come up to temp.

Paul48

It's a 3-pass boiler, and is designed to scavenge heat from the return water. I wouldn't worry about return temperatures. A 200 foot zone may be pushing the limits of the 007. I'd try a VT2218 on that zone. You should be right about at it's sweet-spot. I'd contact Taco, you might even be able to use the housing from the 007 for the 2218.