HOT WATER SUPPLY SYSTEM 1

[Mr.zoro]

IF WE HAVE 2 HOT WATER SUPPLY (HWS) NETWORKS WITH DIFFERENT TEMPERATURES 60& 80 DEGREE CELSIUS
CAN WE MAKE ONE COMMON HOT WATER RETURN LINE COMBINED FOR THEM BOTH ?


2- REGARDING THE HOT WATER RETURN... IF WE HAVE ONE HWS MAIN LINE WITH MANY BRANCHES TO PLUMBING FIXTURES
IN THIS CASE, IF WE USE DIRECT RETURN WE HAVE TO TAKE RETURN FROM ALL HWS BRANCHES WITH BALANCE VALVE NEAR THE END OR

OT TAKE THE RETURN FROM THE END OF THE HWS MAIN LINE ONLY ?

 

[PEDARRIN2]

1. I am assuming if you have more than one temperature hot water system, you have at least one (maybe two) thermostatic mixing valves. It would be preferential to have multiple return systems so you do not return water hotter than your supply. However, if both returns come back directly to the water heater, you should not have an issue. I don't recommend this, because typically part of the hot water return is mixed with the cold water supplying the mixing valve. In periods of low (no flow), the temperature of the return can exceed the temperature of the mixed hot water and you could exceed your design temperature in the lower temperature system.

2. It depends on how long your branches are. If they are less than the code maximum length for unrecirculated hot water (50 ft in the current IPC), then you would not have to provide a separate balancing valve. If the branch does exceed the length, you have to provide the balancing valve.

 

[dbill74]

1. How are you controlling the hot water circulating pumps? If you want to save on energy and circulate water based on the returning temperature, then NO a combined line will not work. If however you are controlling strictly via a timer regardless of return water temperature, then see Pedarrin2's response.

2. What Peddarin said. One caveat, last I checked the less used Universal Plumbing Code (UPC) requires circulated hot water to within 25 feet. Check your current governing code.

 

[PEDARRIN2]

If the circulating pump is controlled by a signal from one of two aquastats (two different temp set points), it could work, although I would not recommend it because the system that did NOT initiate the pump will have flow regardless of the temperature.

Depending on the size of the system (and the building), running the pump continuously is not going to be a big energy drain. These pumps are typically use energy measure in watts, not horsepower.

Again, I would not recommend a combined system - too many things to go wrong and you get the blame.