No flow through baseboard loop?

zepfan · February 10

the above picture is a three zone baseboard system, one zone is for the top level, main level, and basement. I did not install the system, but have worked on it and the boiler for the last 7 years and out side of normal maintenance on the burner, and purging the zones of any air annually, have not had any issues.
What is happening now is the top level (about 15 feet above the boiler ) is fine, as well as the basement, good flow, good heat.
the issue is there seems to be little flow through the main level, which is maybe 4 feet above the boiler. The supply is the one on the far left in the picture, and that loop’s return is on the far right in the picture. I initially after purging the zone and had got very little air out of it, I thought the zone valve was faulty. I installed a new zone valve, and actually tested the new one before pressing it back into the system, to make sure it opened.
That did not resolve the issue. You can not hear any air when the circulator is running, (Taco 007) and weather one zone is open, or all of them, the amps on the circulator, does not change. I would think that a severe restriction in the piping would cause the amps to go down, if the other two were closed?

It seems to me that there is a restriction in that one loop? The only thing I can think to do would be to close the ball valve for that zone, , cut the pipe directly above it, attach a fitting, and a garden hose to it, connect the other end of the hose to city water pressure, and see what the flow is from the open boiler drain on the return side of that loop? The small shut off valve directly below the boiler drain would be closed of course. I have never had copper tube baseboard become restricted, especially when none of it goes under concrete. The entire loop I would estimate is about 80 feet in length.
Any suggestions would be much appreciated. Thanks to all

Big Ed_4 · February 10

Your pipping is incorrect ,

Big Ed_4 · February 10

Your supply for 3 zones is only 1" .. Should be 1 1/4"..

Look up "Reverse Return" when you repipe ..That is another issue..

All the mistakes show up on the coldest day of the year …

Stay warm

zepfan · February 10

thanks, but I don’t know how this has worked for 50 years if the pipe is too small?

zepfan · February 10

Also if the upper, and lower floor’s zone valves are closed, there is still little flow through main level. At that point 1” pipe should be more then enough

Big Ed_4 · February 10

If you close the other zones and still a problem , well maybe there is some blockage , .. When purging is there a difference in water flow out of the hose from the other zones ?

Grallert · February 10

It's super rare to have a blockage in what I am assuming is fin tube. I would strongly suspect air in that loop. How it got there? No idea. Have you closed the other loops and purged the troublesome loop separately?

zepfan · February 11

thanks to all that responded. As it turns out there was a blockage of ice in one of the fin tubes. I went by the home this morning in put a heater in a utility room that has three exposures to outside. I felt that if a pipe was frozen that would be the area of the loop. By 11am the homeowner texted me, and said the room thermostat was up to temperature, and the return line for that zone was hot.

I suspect that at some point over the weekend that the homeowner either mistakenly turned off the thermostat for that zone, or the home lost power. That is the only thing that I could think of that would cause a pipe to freeze with a couple of hours. It was well below freezing here over the weekend. air, and wind must have gotten to those pipes at sometime

either way it is working now and I think some insulation is needed in the wall.

Thanks and take care all

Big Ed_4 · February 11

Ice can cause a no heat but not enough heat call will be other issues ..

No flow through baseboard loop?

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