Advice on hydronic baseboard heating needed.

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Old 12-20-16, 10:51 AM
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Advice on hydronic baseboard heating needed.

I seem to have a mystery in my hydronic heating system and wondered if you can advise and/or point me nearer a solution.

I have a small, two story 1500sqft house with basement and use a small high efficiency condensing boiler.

From the boiler I have Taco 0011 circulator (the only pump in the system) pushing hot water into a 5 outlet manifold of 1.25" pipe. Each of the 5 manifold outlets feeds a 3/4" copper pipe going to baseboard heat and a DHW heater. Each outlet has a control valve activated by the thermostat in each zone.

Output end of the supply manifold is tied in to the return manifold (with a manual controlling valve) as recommended by the boiler manufacturer.

Everything worked as expected (whichever zones called for heat, received heat) until I lowered the manifold from near the basement ceiling about 30" in an attempt not to have pipes and manifold hanging from the ceiling for better sound insulation to the rest of the house from the circulating water.

Now the problem. Unless the second story is the only zone calling for heat and I restrict the circulation from the supply to the return manifold, no heat circulates to the second floor.

I have flushed the system several times to be sure there no air in the system.

I do not know what the pressure gradient across the manifold looks like but I am assuming that there is higher pressure in the supply manifold than in the return which should circulate the water.

The only thought I have on the situation is whether of not the additional 30" of height that I introduced has created too much of additional head for the pressure differential to manage? The second floor baseboards are about 12feet above the circulator and supply manifold.

What else should I consider?

Many thanks for any advice. Dave
 
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Old 12-20-16, 06:18 PM
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If you are hearing water circulate you could have pump cavitation. Increasing the system pressure might help but probably not. A 0011 will move a lot of water. If you hear the noise with only one zone calling for heat, the problem is almost certainly cavitation.
 
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Old 12-20-16, 06:31 PM
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Thanks for your comments, Grady, but I have moved everything as described and am now looking to solve the circulation problem I described.

Thanks again, Dave
 
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Old 12-25-16, 08:06 AM
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I know this is going to sound so basic but have you confirmed the valve for upstairs is opening?
To do so, trace the pipe with your hand to feel how far from the boiler it gets hot.
 
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