HOT WATER SYSTEM QUESTION

[bluenote49]

While we are flushing our HWT system with domestic water for two day in a row, I noticed that the temperature of the circulating water just increased. I do not understand how this happen because we bypass the heat-exchanger in the system so the water is only circulating from the pump to the branch line going to AHU's and the coming back to the pump. Is there an explanation about this one? Can somebody tell me what just happen.

 

[EnergyProfessional]

by flushing you mean you bring in new water and flush the old out? then you shouldn't really increase temp a lot. If you recirculate, the pump may add heat over time.
ho much more temp are you talking about? 1°F, 100°F?

 

[bluenote49]

YES and the temperature of the water is more or less half the boiling point.

 

[willard3]

You are, then, running the water through a heat adder. Heat does not create itself.

 

[IRstuff]

"circulating from the pump to the branch line going to AHU's and the coming back to the pump."

Is the water going THROUGH the AHUs?

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[bluenote49]

"circulating from the pump to the branch line going to AHU's and the coming back to the pump."

"Is the water going THROUGH the AHUs?"

Oh sorry I have to correct that because actually the AHU's are isolated so the water is only circulating in the piping network. Is there a relation between the increased of the temperature of water and water going inside the ahu's?

 

[IRstuff]

" Is there a relation between the increased of the temperature of water and water going inside the ahu's?"

Isn't the whole purpose of running cooling water to the AHUs to transfer heat from them? Are they located on the roof; exposed to sun? Are the pipes leading to them exposed to sun or warm environment?

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[bluenote49]

All pipes are with insulation and cladding and AHU's are located in both the roof and basement. The thing is the the medium w/c is a domestic cold water that we are using for flushing is having a normal temperature and its only circulating on the HWT PIPING network bypassing the H.E. and AHU's. In our design, for the water to increase its temperature it has to passed through the H.E. but in this case since its purpose is only flushing I isolated the H.E. So from my understanding it doesn't matter if the water will go inside the ahu since its not passing through a HEAT-EXCHANGER the temperature of the filling water line(Domestic Cold Water) should be the same with the circulating water temperature in the piping newwork. Your free to correct if I'm wrong. I just want to know and understand what's going on .

 

[chicopee]

Pumping recirculated water will increase its temperature if there is no other heat transfer mode. The pump impeller and flowing friction add heat to the water.

 

[DRWeig]

I agree with Chicopee. Something like 30 to 50 percent of the input power to the pump is going into the water as heat.

Best to you,

Goober Dave

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[IRstuff]

Vitamix, et al, do demos at Costco were they make hot soup solely in the mixer

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[317069]

Herrkaleun asked you if you bring new water to replace the old water, you said yes , it does not mean you are circulating the water,
is your heat exchanger ON or Off, is there any possibility of water to leak through the exchanger?