Gravity System to pump circulated system.

PlumberPaul

I have all of Dan's books and in one of them it talks of the steps to aid in piping and pumping a system that was gravity and will now be pumped circulated.  I was hoping that someone could remind me which of his books has that info so I can reference the book.  If I am not mistaken it recommends that the larger sized piping be reduced considerably at the "near boiler" piping including the pump location.  Any input?

Thanks,

PlumberPaul

DanHolohan

It's in my book How Come?

Thanks for reading me! 

Mark Eatherton

Is this it???

Existing pipe size, divided by 2, and then the next pipe size down from that...



For example, if the gravity main is 4", then 4 divided by 2 = 2, and the next pipe size down would be 1-1/2". So your near boiler piping would be 1-1/2".



You also don't want to use a high head pump, because the gravity is still there. It just needs some assistance when first starting up cold.



Frank "Steamhead" Wilsey also has an excellent article that he wrote pertaining to the pump sizing.



If the house is multiple story, you also need to be aware of the possibility of restrictive orifi in the upper radiators. If there, you will know because the upstairs will not heat right, and the lower floors will over heat. You may have to locate them and either eliminate them, or switch them to the lower floors to balance out the system.



Good luck.



ME

Mark Eatherton

Timing...

is E V E R Y T H I N G ;-)



ME

PlumberPaul

That's it....now the next question.....

The job is a large one-family house in Manhattan.  The system now has two large mains leaving the boiler and the boiler room.......One is 6" and the other is 4"

If I wanted to have a single pump.....pumping away from the new boiler......and after the pump connect to the two mains, what do I use as pipe size? 

Many thanks for the help.

DanHolohan

I would use 2-1/2"

Based on the old rule of thumb.



Other opinions happily accepted!

Dan C.

Article

Speaking of that article, where can I find it? I was looking for it a couple of months ago and couldn't find it by searching.

Mark Eatherton

Well....

I know it is on this site SOME where, but here is a link to another site that posted the same article.



http://www.masterplumbers.com/plumbviews/2003/sizing_circulators.asp



Maybe Frank will come by and give us a link to the article on this site.



ME

Steamhead

It's here:

Thanks for the kind words, ME.



http://www.heatinghelp.com/article/343/Circulators/238/Sizing-Circulators-for-Hot-Water-Heating-Systems



Basically, you size the circ to the installed radiation while sizing the boiler to the building's heat loss. The circ is sized to mimic the gravity flow rates. I tried this on my own system first, then some other systems before writing the article ;-)



Dan's method did essentially the same thing before small wet-rotor circs became common. The smallest ones available at that time were the B&G 100, Taco 110 and similar 3-piece units, so he told us how to make the best of what we had then.



You might also be interested in this thread, which shows how water flows thru over-pumped rads as opposed to properly-pumped ones:



http://www.heatinghelp.com/forum-thread/140472/Seeing-Inside-an-Over-pumped-Radiator

NYplumber

Constant

Since you are dealing with a large volume of water, constant circulation is key. If I recall correctly, icesalor has some photos of his 4 way mixing valve applied to gravity conversions.