Combined Hydronic Piping

[madvb]

Hi all,

Has anyone done a combined hydronic space heating and domestic hot water piping? I have a boiler that will provide heating to my VAV boxes while running its hot water through a heat exchanger for domestic hot water. I am having a hard time coming up with a schematic diagram that will show how this system is controlled, the number of pumps needed, the sizes of the pumps, where to put the control valves, etc.... Has anyone done something similar and is willing to share his/her knowledge?

Thanks.

 

[TBP]

You could try the ASHRAE books, or if you just want nice, simple "cut to the chase" info, go to

http://www.heatinghelp.com

There's a message board mostly populated by contractors who do residential hot water & steam heating, and another section with inexpensive books.

 

[Joesteam]

You will need two separate loops, one for the domestic hot water and one for the heating. I have used a mixing valve on the heating loop to control the temperature of the heating water as the boiler water must always be the same hot temperature to create the domestic hot water.

 

[Zapster]

http://www.tekmarcontrols.com/literature.html

show some schematics

 

[borgafied]

be sure to pay attention to pressures in the system if you decide on more than one circulation pump (one for the domestic water, one for the hydronic heating system, etc). also make sure that your boiler is getting the right amount of water flow, at the correct temperature

i have been trying to find this information also, and have found it very difficult to find. the boiler mfg's don't publish much info, and the heat exchanger mfg's don't go into enough detail to be of much help.

 

[imok2]

This is a handy web site for engineers and it may help you find what your looking for:

http://wea-inc.com/mainfrm.htm

 

[Drazen]

Several companies that offer combination heating/hot water boilers have prepared layout for piping/control of such system. It is based on use of "hydraulic switch". Priority is given to hot water consumption and pressure loss, when opening hot water tap, triggers "switching over" to hot water heat exchanger. However minimal circulation in heating system must be maintained to avoid hydraulic hammers.

Try this:

http://www.diyfaq.org.uk/plumbing/combi.html#pressure

New Audel HVAC volumes (all three) give some very usefull data on switches and all components.

http://www.amazon.com/exec/obidos/s...vance-above&field-keywords=audel hvac library