Gravity hot water conversion

D Shedd

I have a customer with a 1912 Capital gas fired (conversion) hot water boiler that is leaking. The system is large pipe gravity hot water with gigantic radiators. The radiators have Honeywell Unique valves with supply and return going into one opening. Can this system be converted to one with circulators, or do these Unique valves pose a problem. This is the first time I've ever seen these valves and I'm the 4th generation in a company started in 1893. Thanks for any input.

clammy

The same

It,s really funny you posted this just last friday i ran into my second unique sytem and she was converted to a pump sometime in the late 50 from the coal boiler to a gas .We are currently going to install a munchkin with a indirect the modulating burner and outdoor reset should save the ho some bucks but it can be done just remenber you don't need a big pump this system was about 9 rads off a 2 1/2 main reduced to 1 1/4 with a b&g series 100 pump .I also had to move 2 rads about 10 ft which was n,t to bad best of luck and yes it can be done plus if your a wet head you can do anything peace clammy

Joe Grosso

Clammy's right

circs will work fine as long as they are not oversized. You want to mimic the gentle gravity flow to keep the water from moving fast enough that it will short-circuit thru the rads.

Count your radiation and take the total EDR to the chart you will find here:

http://www.heatinghelp.com/newsletter.cfm?Id=125

This will tell you what circ to use on this system. It may seem tiny compared with the (oversized) ones we usually see, but you'll love the way it works.

Note that even if the heat loss is less than the EDR, you still size the circ to the radiation. Of course you'll size your boiler to the heat loss, but that has nothing to do with the amount of radiation.

D Shedd

Gravity hot water

Thanks for the good advice. Do I understand you correctly that the large mains (2 1/2") don't have to be changed?

Mike T., Swampeast MO

No you don't want to change the mains.

Do do though need to downsize the near-boiler piping. The rule of thumb is ½ the size of the mains minus one more pipe size. For 2½" mains this means 1¼ - one pipe size = 1" near boiler piping.