140 Deg. Domestic & Hot water heating system? 1

[buildingconsultants]

As part of a new condominium development, it is being suggested that we combine the domestic and hot water heating equipment into one system for a discharge temperature of 140 Deg. F. What are the cautions to design and install a system such as this?

 

[235zzzo]

Hi Buildingconsultants!!
If I understood your question, it is quite possible to do so! You have to consider:
For security and efficient reasons, use only one heat source, a gas-boiler (with (or not) a thermal inertial tank), which will produce all the heat needed for:-
1. the heating system of the building, sub-divided into domestic areas and common areas for each floor; Therefore you have to provide the supply closed-circuits to the terminal dissipation equipments. The temperature, 140ºF (about 60ºCelsius) can be consider appropriate for central heating purposes.
3. Likely, depending on the same boiler, you have to provide another closed-circuit, that is a primary circuit to serve a heat-exchanger or a tank-heat exchanger, which its secundary-circuit, will be conneted the domestic hot-water supply system of the building. With an automatic thermostatic three port valve, temperature probe and electrical actuator, you can set the most convenient temperature, that is some value in-between 113 ~ 118 ºF;
4. Finally, for a condominium, you should provide the installation of automatic counters for each domestic and common areas, unless you don't want to prevent those interesting long meetings, each quarter of the year.
Hoping this can help.
zzzo

 

[235zzzo]

Hello Again Buildingconsultants
I just saw your question and already some answers in the other forum, "Pipe & Fluid Mechanics" and let me add some details, which have to be considered in such installations design/project:
1. Of course, the pressure field in the heating system closed-circuits, are normally lower than in the domestic hot-water supply net-circuits, because the last need higher pressures for their function. But again, there's no problem, because physically those circuits are separated at the heat-exchanger system. You can have 30 psi in one side and 100 psi in the other side.
2. In order to cope with the dead water in the domestic hot-water supply pipes, there are some easy/simple solutions, which are in common use, that is to consider a small circuit shall we say, of a 3/8" Diam., to link all the consumers, specially those located far away from the central, with a layout in a reverse sense (closed-loop) returning to the entrance pipe at the secondary heat-exchanger circuit. Of course you need a small re-circulation pump to provide a flowrate, which dimensional criterium is based on the wall piping thermal losses you have, to keep the set hot-water temperature, at all the consumers.
zzzo

 

[buildingconsultants]

Thank you 235zzzo for your input. It was indded a great deal of help in understanding how the system will develop.:-9

B

 

[TBP]

Using heat exchangers to separate the two water loops is the traditional method of designing these systems. However, the boiler water will have to be somewhat higher than 140*F, likely at least 180*F. The closer to domestic water temperature the boiler operates, the larger (and more expensive) the heat exchanger must be.

I took the question to be one of having the heating and domestic water loops as one and the same. If that was correct, then I think you'll run into no end of jurisidictional disputes between the plumbing code requirements and the boiler/pressure vessel/power piping inspectors. You'll either be caught in the crossfire because everybody is claiming jurisdiction, or the project will be orphaned because everybody says it's somebody else's job to inspect. Good luck.

 

[235zzzo]

I agreed with TBP, you should have a higher temperature in the primary loop, (which goes directly into the boiler), something in-between 170 and 180 ºF, but no more, because shoulde pay attention, that the primary-loop links all the terminal heating equipments, if nearby the persons.

Concerning the other eventual conflits, that you mention, the most rigorous criterium/code should prevail in such "hybrid" zones of those installations, (usually, the code implies the minimal requirements, if you do more and better, better you do!...). The other thing, which can be suggested, is to study and write down a suitable protocol of common sense rules, make it approve by all along the process, in the project, for the installation and for the running-operation procedure by the condominums.
zzzo