Size of pipes in forced water heating system

Bill de Rosa

Thank you again. I find your replies very helpful.
As you have been so kind I would like to take further advantage of it.

What are the balance considerations which come into play?? Also is there a place, like the one you gave me for the gravity system, where I can learn the basics of a forced water system?? I have quite a few questions that come to mind, such as circulator type and size, kind of pipe material (i.e. iron vs copper) and so on.

For what professionals are concerned, I am quite discouraged, that is the reason I am attempting to learn as much as I can. It seems that everybody is interested in changing the boiler, but nobody wants to mess with the plumbing. I have had three H/C companies look at the system; they all gave me different answers, nobody even mentioned what, after following your suggestion and reading about the gravity system, seems a quite obvious thing: I have a system converted from "gravity" to "forced". I apologize for venting my frustration, but I was trying to explain why I am attempting to learn as much as I possibly can.

Than you again.

Bill de Rosa

Pipe sizes in forced water hydronic system

I need some help!! I am refinishing the basement in an old brick building with forced water heating system. The building is two floors high on top of a good height basement. The pipes (cast iron) carrying the water from the boiler start at 3/4 at the boiler and increase to 3 to 4 inches along the basement ceiling, before being reduced again to 3/4 as they start rising toward the first and second floor. The return pipes enter the basement at 3/4 and expand to 3 4 inches along the ceiling before being reduced to 3/4 at the boiler return manifold. What is the function (if any) of such large pipes?? I would like to change them with 1" pipes so I can gain some head space. If I do that will there be enough heat still carried to the first and second floor??

Thank you in advance for your ideas.

DanHolohan

Sound like

you have an old gravity hot water system. You can read all about it here (cut and paste)

http://www.heatinghelp.com/heating_howcome1.cfm

Bill de Rosa

Thank you for your reply. I have followed your suggestion and read about the gravity system. It gives suggestions on how to replace near-boiler pipes.

My question is: can I change all the pipes running along the basement ceiling using the same formulas without interfering with (and eventually improving) the heating efficiency of the system??

Thank you

DanHolohan

Those rule

apply to the near-boiler piping. You can reduce the size of your basement pipes if your system has a circulator, but the size would be based on the flow rate, which is based on the heat loss. One-inch pipe, for instance, has a maximum flow rate of 8 gallons per minute. Based on a 20-degree temperature drop across the system, that represents 80,000 BTUs per hour, which is quite a bit.

If you're not comfortable with the sizing, it would be best to have a pro look it over and make recommendations. There's also the issue of system balance to consider.

Thanks for the good question.