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Old 11-17-2008, 06:22 PM   #1
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radiator system unequally warm despite bleeding


i have bled all the rads, yet the system is not hot equally all over. i also have run pipe for two new rads without actually mounting them on yet, could it be that the branches are creating air pockets that bleeding the installed radiators does not help against ?

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Old 11-17-2008, 07:03 PM   #2
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radiator system unequally warm despite bleeding


you might get more help posting this in the hvac section. Having added to your system, you'll need to know if your system can handle it. Smart guys and gals over there, good luck

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Old 11-17-2008, 07:18 PM   #3
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radiator system unequally warm despite bleeding


you might of compramised the flow on the others with the add on....can you shut the new ones on the supply valves to see if the original heat up
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Old 11-17-2008, 07:34 PM   #4
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radiator system unequally warm despite bleeding


What type of hydronic heat do you have; Baseboard radiators or cast iron radiators? How did you plumb the new radiators; in a series on a loop or parallel?
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Old 11-18-2008, 09:06 AM   #5
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radiator system unequally warm despite bleeding


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Originally Posted by Clutchcargo View Post
What type of hydronic heat do you have; Baseboard radiators or cast iron radiators? How did you plumb the new radiators; in a series on a loop or parallel?
cast iron. i followed the same pattern as the rest of the rads: the inflow coming from the inflow main and the outflow going into the outflow main. i do not know how that relates to your options.
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Old 11-18-2008, 02:11 PM   #6
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radiator system unequally warm despite bleeding


Gotcha,
are the rads that are staying cool furthest from the boiler as far as the circuit is concerned?
I'm thinking that you either need a bigger pump or you need to restrict the flow to the rads that are closest to the boiler so that some of the hot water can get to them. I think the water is taking the easiest route back to the boiler.
Also, if this is a conventional boiler, keep in mind that you need to maintain at least 130F(Oil) or 140(NG) return water to the boiler when it's running. Adding the extra rads to the circuit may drop you below these temperatures. If it's a NG high efficiency condensing boiler, then no problem.
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Old 11-18-2008, 02:40 PM   #7
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radiator system unequally warm despite bleeding


there is no additional radiators on the system relative to last winter, only the outlets. for one of them, the branch (both pipes) runs about 15 ft, the other barely 3-4. both are capped at the ends. could it be that the air pockets inside them are expanded into the mains they branch out of and that are impossible to bleed at this point are causing the poor flow ? because, really, the boiler is in the basement roughly in the center. from it, both the in and outflow pipes split two ways to both sides of the house. both new outlets are on the side of the house/boiler that remains cold. the unaffected side is as hot as it can be. however, what still puzzles me is that i did successfully bleed air out of every radiator.

having established that, i doubt it is the pump but, if it is, i wonder if it is easy to replace it DIY ?

thanks much.
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Old 11-18-2008, 03:06 PM   #8
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radiator system unequally warm despite bleeding


If that's the case then you definitely have air stuck in there someplace. Can you close down individual radiators and bleed one at a time? Eventually, all the air will dissolve into the water and get taken out by the air trap.
I installed a temporary baseboard system in my house on a single loop. Even though it's possibly an idiot proof system and I thought I had all the air out if it, it still didn't get hot. I had to run water through it for 30 minutes before all the air got out of the system and it actually got hot.
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Old 11-18-2008, 04:02 PM   #9
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radiator system unequally warm despite bleeding


clutchcargo, i doubt that any of my radiator valves are working, they are old and look painted over multiple times.

also, could it be that the sequence in which the radiators are bled out matters, i.e. if going out of sequence reintroduces air in previously bled out rads ?
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Old 11-18-2008, 08:57 PM   #10
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radiator system unequally warm despite bleeding


could this be due to the expansion tank? i had to change its position as well.
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Old 11-20-2008, 08:49 AM   #11
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radiator system unequally warm despite bleeding


I assume the expansion tank is one that has a bladder, it's not an older expansion tank is it? If it is it could be the source of trapped air and you should replace it with a new one. Other than that, i suggest just let the water run for 30 minutes. Llike I said, I have a simple system but I couldn't get the air out until I finally just wasted some water.
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Old 11-20-2008, 09:06 AM   #12
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radiator system unequally warm despite bleeding


mysteriously, this is now working fine. i was all bummed yesterday and frustrated i could not understand the physics behind the poor circulation on one side of the system and getting ready for another futile night of attempts to fix it, when i got home and realized it all works

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