I have a 4-pipe heating/cooling system in a church. One of the fan/coil units is experiencing extremely low flow rate through the hot water coil. All the other fan/coil units work OK. I have blown high-pressure air through the problem coil and feel confident that the coil is not blocked. What are problems that could inhibit water flow through a how water coil that is not blocked? Any ideas would be apopreciated.
Extremely Low Hot Water Flow Through Fan/Coil Unit
Joe Howell
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I have a 4-pipe heating/cooling system in a church. One of the fan/coil units is experiencing extremely low flow rate through the hot water coil. All the other fan/coil units work OK. I have blown high-pressure air through the problem coil and feel confident that the coil is not blocked. What are problems that could inhibit water flow through a how water coil that is not blocked? Any ideas would be apopreciated.
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Thanks....I can try to get Regulated Nitrogen of CO2 to do this. Also curious about why blowing compressed air through the coil would not do anything??
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Is it the coil or the supply return piping?
Pressure gauges and thermometers are needed!
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It is the coil. There is plenty of flow through the hot water bypass pipe when the thermostat is not calling for heat.
However, when the thermostat calls for heat, the inlet pipe to the coil becomes hot and the coil becomes warm on the bottom (near the inlet), but becomes progressively cooler toward the top of the coil where the outlet pipe is. It seems that the flow is restricted.
However, when the thermostat calls for heat, the inlet pipe to the coil becomes hot and the coil becomes warm on the bottom (near the inlet), but becomes progressively cooler toward the top of the coil where the outlet pipe is. It seems that the flow is restricted.
Pull the coil out and take it outside, pipe it up so you can flush it with a hose both directions it to a bucket to catch what ever is causing the blockage. That way the water treatment company can address the root problem. The flush with a hose provides enough volume to get in to each pass. The unit should have a tag stating max pressure more then likely since one end is going into a bucket you won’t exceed that pressure. Trust me take it out side if you try it in place you don’t have enough rags to clean up the mess when the loose hose comes out of the bucket.
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Since you mention hot water bypass pipe, I take it that the coil has a three-way valve. Is it operating properly? Is it properly installed, with the ports piped up to the proper connections?
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How do you know the GPM's? Are there pressure gauges?
I agree with Nuclrchiller Could be an issue with the control valve!
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Yes, you are right about it having a 3-way valve for hot-water bypass. This valve is installed and operating properly.
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Can you draw out the piping, all the way back to the source of the supply and return.
Start there.
Perhaps a strainer is clogged.
Its almost impossible to tell if flow is good during bypass.
Also - is this coil larger or different in some way from the others.
Is the valve on the supply side or the return side.
Has it been replaced recently?
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Is there a balancing valve?
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Whats the system pressure, and how high up is the coil?
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The balancing valve on the hot water outlet pipe is fully open (as is the shut-off valve on the hot water inlet pipe). I am not familiar with balancing. How can I determine if a balancing issue may be the cause of the low water flow through the coil?
Thanks.
Thanks.
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No thermometers or pressure gauges on this coil. We have 54 of these fan/coil units throughout the church where this system is installed. This fan/coil unit seems to be to only one with flow problems through the coil. The bypass pipe gets plenty hot when the thermostat is not calling for heat leading me to believe that the three-way valve is working OK. System has been running since 2004.
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