Radiant loop flow

Jeremy in DM

correct, he would have to add another pump, which is exactly what the Taco intruction sheet shows.

I see your point that it is 'pulling' out of the high temp loop, but what is it pushing into? some goes back into the mixing valve, and some is put back into the high temp loop. Since the other high temp zones are not secondary piped, the all become part of the main loop. so what is not pumped back into the mix valve is pumped into the main loop and all the high temp zones.

Unknown

How is he circulating through the high temp zones? the water hits the main headers, circulates back to the supply side, where it is pulled through the mixing valve in the same volume it is being returned to the supply header.

there is an off chance of some flow induction through the high temp zones, but nothing that would affect the head loss visible to this pump.

Jeremy in DM

it seems to me that what is not put back into the mix valve goes back into the main loop past the boiler to get reheated, correct? so, the boiler pulls water out, heats it and puts it back in. the high temp zone pumps pull hot water out of here, and put it back into the return. since those high temp zones are not piped secondary, which is not incorrect, and the high temp pumps are not running, water does not flow past them, the way it would if you had to tee's close together.

even if the resistance is less going past these and back to the mix valve, which there is no guarantee, it still goes through extra piping, and the strainer. if the mix valve was secondary piped, and another pump was added to the main supply, the pump for the mix temp zones would only flow within those zones, not the entire system.

what you would have then is the main loop pump would run parallel to the mix temp pump, and in series with the high temp zone pumps.

this may not be the actual cause of his problem, but it could be a problem, because i really feel that his current piping is not correct.

Unknown

water will flow past the pump intakes going to high temp even though they are not primary/secondary, no problem. The only issue is the possibility of flow induction due to the pressure differential at the supply and return for each high temp zone.

But nothing stops the flow from just screaming past the high temp supplies on to the mixing valve. At worst, the pumps could fight. they probably won't. it's certainly not the cause of this problem. It could not possibly be. and frankly if the pumps won't fight in this case, I applaud him for ditching an unnecessary pump.

MikeyB

i-valve

Jeremy, that pic you have pointed out is a Taco I-Valve not a Taco 5000 thermostatic mixing valve like the one John installed

Unknown

or

the calibration on the scale is wrong on them or Viega got a bad batch from the OEM, who knows? It's just another possibility of many and I'd hate to see the guy do a lot of extra unecessary work, that's all. If it was me, I'd let the system run a couple days and make sure I'm not chasing ghosts. If it doesn't perform then I'd start looking at tearing things apart. Maybe I'm too much of an optimist.

The trouble is, it's tough to troubleshoot on the net, I wish I was there looking at it for myself.

John M_5

All right George just for you , I pulled apart the mixing valve no silver bullet. Also remove the flow check, no change. Personally I leaning toward the F’ed up Flow meter Theory

John

Unknown

We ain't outta the woods yet,

let's wait and see how it does over the next few days.

George Peteya_3

Thanks John ...

... one more possibility off the table. I never could find those x-ray glasses.

Jeremy_14

To everyone other then John, six faulty flow checks, huh??? He's already told us his serveral 280' curving, couplinged, maybe kinked at one time loops flow at a much lower rate then his 160', 170' loops are with little change regardless of pump ability. All the pumps and valves are unibstructed as he has checked them all.

To John,okay so Viega has told you your loop lengths are fine, must be some other issue hmmmm? How about trying my temporary 3' circuit idea for one loop. I'm just saying, I don't think all your loops will flow at the same .08 gpm unless you want to change the way your system is piped. Different pump for each manifold? Common supply.

Jeremy_14

Low Flow

To everyone other then John, six faulty flow checks, huh??? He's already told us his serveral 280' curving, couplinged, maybe kinked at one time loops flow at a much lower rate then his 160', 170' loops are with little change regardless of pump ability. All the pumps and valves are unibstructed as he has checked them all.

To John, okay so Viega has told you your loop lengths are fine, must be some other issue hmmmm? How about trying my temporary 3' circuit idea for one loop. I'm just saying, I don't think all your loops will flow at the same .08 gpm ever unless you want to change the way your system is piped. Different pump for each manifold? Common supply perhaps? Or wait until the dead of winter next year to see if you can be happy with what you have now.

Unknown

I myself,

asked my local design helper about 280' loops. He shook his head, not a problem he said. John figured the head loss into his pump selection so flow should not be an issue there. All I'm saying is just because those flow meters have a scale on them it doesn't mean the calibration is correct. Like the old Honeywell round T'stats. Just because you set them for 72* that doesn't mean you'll get 72*. Once he's let the system run and settle out he needs to retake delta T using the same thermometer for both readings. Once he has that, if it's still excessive, he'll need to look further into the system. 10-15* on a system that has only been running a few hours seems ok to me but only time will tell.

John M_5

Just want to say THANK YOU to all. I will let it run for a while. And see how it goes. The weather here is getting warmer, lows only in the 30’s I’m in New York. So I may have to wait until next season for a true test. So far the fan Coil has been doing a fine job. I pulled out a 100k BTU furnace, 70k BTU boiler and 40k Btu water heater. Replaced by one 106k BTU Modcon, so it can’t be any worse. Nothing like a challenge to get the brain juices flowing. Thanks Again.

John M

P.S. I will let everyone know how it goes.