Monoflow Loop Problem

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Old 12-24-06, 07:58 AM
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Monoflow Loop Problem

I am having a problem with a monoflow loop. Some of the radiators off of the loop are not getting hot. Here is the setup:

Primary/secondary system. One zone off of this system is a monoflow loop built in the boiler room consisting of Taco 007, Flowsetter, 1" tubing and 7 sets of B&G monoflow fittings installed back to back (rings on the fitting next to each other). The output side of the monoflows go to PEX which goes to Buderus panel radiators with diverter valves. On the two panel radiators that don't heat, the diverter valves at the radiator barely get hot and the PEX return at the monoflow fitting is cold and the supply at its fitting is hot.

I have checked the Buderus diverter valves because there is an adjustment as to how much of the water into the valve goes to the panel radiator as opposed to being returned thru the valve. I have tried both the full bypass or 50% to the radiator adjustments and there is no difference, the water still does not flow in this loop. Most of the takeoffs from the monoflow fitting have ball valves so I have closed all except for one of the radiators that does not heat and that makes no difference. The radiators that don't heat are the last in the loop and one in the middle of the loop.

The system was operating fine until earlier this year when the Buderus atmospheric was replaced by a GB142. I have been bleed air from the system at the radiators but most of it is out now although you can still hear some air noise in the pipes in the boiler room. The Spirovent should take care of the rest.

The only thing different is a different antifreeze than before. Any chance this affected the pumpability of the water and the 007 is no longer up to the task? Since most of the radiators off of the monoflow loop work fine, this seems unlikely. Could the loops off of the monoflow loop that don't heat still be air bound? Could I have radiator diverter valves that got clogged or became defective? For what it is worth, B&G lists the Cv of a set of 2 fittings as 8.7. The PEX loops to the panel radiators are approx 50' to and 50' from the panel radiators.

Any ideas would be much appreciated.
 
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Old 12-24-06, 09:16 AM
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Monoflo woes

#1. You need to bleed/purge until you know for sure that air is not the factor.

#2. If you still have sporadic flow, then I'd suspect that you don't have enough velocity for the Monoflo fittings to properly divert water to the branches where you need heat to flow. If that were the case, I'd get a small Grundfos 3-speed. I think they're quieter than the Taco and also have more flow at medium and high speed settings. $100 at the supplier and a half an hour to swap out the 007 (possibly the impellers are worn?).

#3. When looking at Cv stats look at what that asterisk means. They only measure the Cv with the side branch plugged. Without it plugged, the Cv is quite low or our systems would never work without mega HP circs.
 
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Old 12-24-06, 11:37 AM
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Monoflo Woos - Taco Swapout

Thanks Who.

I had gotten a similar suggestion about putting in a Grundfos 15-58 at The Wall forum. With the three speeds and three different pump curves, it has a lot more range than the 007. I really suspect the different antifreeze has something to do with the viscoscity of the fluid in the system.

Do the Grundfos use the same flanges as the Tacos?
 
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Old 12-25-06, 11:16 AM
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Same

Yes, same flanges - all small circs are 6.5" between the flanges.
 
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