Radiant Heating loops not getting hot enough

smurfy82

I have recently installed a Navien NCB 240E with 4 radiant zones and 2 baseboard zones although the baseboards are currently not hooked up. I have ensured that none of my loops are more than 300 feet and there are no leaks. Each loop has its own TACO 007 circ pump. The boiler is constatnly short cycling (running for a minute or less and then shutting down for about 3 minutes before starting up again). The navien manifold legs are much warmer than the supply for the loops. I am wondering why I have such low flow or heat exchange. I have tried to bleed the loops a few times and it appears to always have a smooth steady flow before closing and hooking back up leading me to believe its not air bound. The only thing I have heard up until this point is that I put my circ pumps on the return side of the loops when I should have put it on the supply side. Navien claims that shouldnt matter however. Does anyone have any suggestions? Thanks.

I have included pictures.

smurfy82

Please check this video for a more complete visual explanation. Thanks very much everyone. https://youtu.be/kJAvkPw4XuE

neilc

you need a circulator on what should be your primary loop, the loop with the expansion tank,
the boiler heat is going down the manifold leg, over 4 inches, and right back into the boiler return,
you need something to FLOW past the manifold legs,

are there other supplies not shown ?
I see 4, and 2 more return circs up high,
and only 2 supplies down low,

and I'm not certain of the primary either,
more pictures, from more distant

kcopp

You will Never pull enough flow through that mixing valve...
Injection piping would be best.

neilc

kcopp said:

You will Never pull enough flow through that mixing valve...
Injection piping would be best.

I kneew there was something else

smurfy82

https://youtu.be/kJAvkPw4XuE

hot_rod

You need some repiping work. A better primary loop piping, and some circulator downstream of the 3 way mix valve.

HomerJSmith

I would have used a Taco I-series setpoint mixing valve. I don't know what the CV of that Taco thermostatic mixing valve is, but I would want the the highest CV that I can get.

Zman

HomerJSmith said:

I would have used a Taco I-series setpoint mixing valve. I don't know what the CV of that Taco thermostatic mixing valve is, but I would want the the highest CV that I can get.

Why not I Series with outdoor reset? In my mind it is a must with high mass concrete and a good idea in low mass system.