Hydronic Heat Plumbing


Old 01-22-03, 12:41 PM
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Hydronic Heat Plumbing

I am the owner of a 80 year old brick, 2 story row house, 1,800 square feet. It utilizes a hot water/cast iron radiator system. The original boiler was coal fired and gravity fed as evidenced by the existing plumbing. The current boiler is about 60 years old with 1 circulator pump. It is single zone. It feeds 10 radiators of various sizes. There is a seperate trunk line for suppy and return. (No continuous loop). All boiler connections are made with 1.25" id black iron pipe. This pipe almost immediately expands to 2.5" id and is reduced as the trunk travels down the line. All branches to and from the radiators are .5" id. I am going to replace the boiler this Spring. I would also like to replace the trunk lines as they are hanging at 6 feet. Do I need to use the large pipe or can I run the trunk at a constant 1" or .75". Can I use copper with brass conectors to the threaded radiator feeds, or do I need to stick with black iron?
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Old 01-22-03, 01:02 PM
Ed Imeduc's Avatar
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Location: Mountain Williams Missouri
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You can go to http://heatinghelp.com This is where all the so call wet heads are its all wet heat ED
Old 01-22-03, 06:48 PM
KField's Avatar
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I'm a wethead thank you.
Rule of thumb is when going from gravity to forced circulation, all mains can be cut in half. So you should consider starting with a 1" main and branch to 3/4" for all runs. Don't cut the 1" runs down to 1/2" or you may have trouble bleeding air later depending on pitch of the pipes. Also plan on using a reverse return system. It is constructed so that the first radiator off the supply is the last one into the return. It adds some material to the job but it puts exactly the same pressure differential across each radiator and eliminates numerous balancing problems later.

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