Are radiant tubing manifolds with adjusting valves worth the cost


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Old 10-26-14, 02:48 PM
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Are radiant tubing manifolds with adjusting valves worth the cost

I have a home with two zones for a suspended 2" slab with radiant heat and R24 in the joist spaces. Zone one has 4 loops and one room with one loop that I want to keep cooler than the rest. Zone two has 4 loops and one room with one loop that I want to keep warmer than the rest. To buy manifolds with adjusting valves (for example Uponor) would cost me about $600. My question is can I get close to the same performance just building my own manifolds using pex and shutoff valves to regulate the flow of water through the different loops within a given zone? Or, are the spendy manifolds worth the price?
 
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Old 10-26-14, 03:09 PM
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shutoff valves to regulate the flow of water through the different loops within a given zone?
You will not meet with much success in any attempt to regulate the heat to a given area by regulating the flow. I know that it seems like it should, but reality is that it doesn't work that way. At least not well enough to justify the cost of the hardware and the labor to make the changes. You'll be unhappy with the results... at best.

Zone one has 4 loops and one room with one loop that I want to keep cooler than the rest. Zone two has 4 loops and one room with one loop that I want to keep warmer than the rest.
I don't understand what you mean...

Is each loop going to a separate room? Is that what you're saying?

So, you want one room out of four on zone 1 cooler, and one room out of 4 on zone 2 warmer?

Do I have that right?
 
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Old 10-26-14, 03:58 PM
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Yes, you have that right. Each room has one loop and there are 4 rooms on one zone and there are two zones. One the first zone we want one room cooler and on the second zone we want one room warmer. I have used the Uponor manifold with adjusting valves before and like how it gives the gallons per minute flow through a given loop but I am wondering how well a basis, homemade manifold would work using shutoff valves to regulate the flow of water.
 
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Old 10-26-14, 04:05 PM
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When you say 'shutoff valves', do you mean 'ball valves' ? If so, they would 5uck. Ball valves are extremely difficult to throttle flow with.

If you are going to use a quality 'globe valve', you might have better success.

But then, how are you going to know the flow that you have? You'll need flow meters, won't you?

And again, I don't think you'll be happy with the results... even if you use the expensive manifolds with the flow meters.

Adjusting heat output by varying the flow is rarely satisfactory.
 
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Old 10-26-14, 04:09 PM
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Ok, thanks for the heads up on the ball valve. I had no idea they were hard to regulate flow with. I have used an Uponor manifold before for the same purpose and was happy with the result so maybe I will go that route despite the cost.
 
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Old 10-26-14, 07:29 PM
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I had no idea they were hard to regulate flow with
The reason is that 90% of the flow regulation occurs in the last appx 15% of handle travel. It's VERY non-linear.

15% of 45 travel is about 7 so you can see how very touchy they are when used for throttling.
 
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Old 10-27-14, 06:10 AM
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The accepted way of controlling the temperature in a heating system is to use thermostats that control a zone valve or zone pump that shuts off the flow of water to the heat emitters in that room once the thermostat is satisfied.
 
 

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