Added 3 T's to end of main loop with 3ft drop - need advice please

cpetro45

Hello, first time poster, and have come across this site multiple times. I'm looking for some advice.

I have a 2 pipe system that has been working great with cast iron rads. I added a manifold at the end of the main loop feed and return with 3 T's spaced about 8 inches apart. All 3 new radiators are bleeding just fine. It seems like I am only getting light flow to the last radiator on the manifold. The other 2 are cold.

Each pex is 3/4 and goes about 15 - 25 feet. The one getting heat on the feed side is the longest run.

The circulator pump is a Grundfos Alpha2 1/16 HP. The boiler is a Well-Mclean 92% efficiency newer boiler.

The main loop appears to be a mix of 1 1/2 / 2 " pipe.

I'm wondering if since these are at the end of the loop, there just isn't enough Head on the pump to satisfy all 3 T's as well as the vertical drop on the main loop?

I was thinking of adding another circulator pump on the return side, near the copper manifold.

System pressure is about 14 PSI. It's a 2 story home, all these new radiators on 1st floor with probably about a 6 ft incline to the rads.

Jamie Hall

Remember that water is very lazy, and will always take the easiest route. Your long extension at the end of the loop and the Ts and the PEX are not the easiest route -- so the water doesn't bother.

You either need to reduce the flow to the other takeoffs on the loop or, as you suggest, add a pump specifically for you new lines.

cpetro45

Jamie Hall said:

Remember that water is very lazy, and will always take the easiest route. Your long extension at the end of the loop and the Ts and the PEX are not the easiest route -- so the water doesn't bother.

You either need to reduce the flow to the other takeoffs on the loop or, as you suggest, add a pump specifically for you new lines.

Thanks Jamie, appreciate the input, indeed that makes sense. I don't really want to fuss with some of the radiator valves as some are old and need replacement so I think I'd just rather add another pump. In your opinion would you put the pump on the feed side or the return side? (Grundfos circulator is pulling away from boiler) I was thinking just pull from the return side. Thoughts? Or do you think it'd be better to add another pump at the end of the feed, pushing through the 3 T's instead of pulling?

Thanks,

Chris

cpetro45

I've decided to add another pump to the feed side before the 3 port manifold I created. I got another Grundfos Alpha2 on order.

I'm hoping this doesn't interfere with flow to the other radiators at the end of the main loop, but since it's a multi speed pump I will either set it at a fixed speed or autoadapt if it doesn't impede system performance.

I did close off the closest radiator at the end of the loop to see if that created any flow through manifolds...it did not (it's piped at 1 inch black pipe)

Anyone have any more thoughts on this? I couldn't find much on having 2 circulators in the same main loop (besides right in line with each other)

Thanks,

Chris