Converted Gravity hot-water system isn't working properly

Larry C_13

I believe that gravity flow systems used orifice plates in the upper floor radiators, to restrict the amount of water flowing to them.

Larry

Robert_25

Converted gravity hot-water system isn't working properly

Hello, this is my first post on "the wall". I am looking for advice on trouble-shooting a hot-water heating system, I believe it was a coal-fired gravity system that was converted to a natural gas boiler with a circulator at some point. The story is rather long-winded but I don’t know what is significant and what is not, so here goes:

This past weekend I stayed with some friends in Rochester, NY; they have a full 3-story home that was built in 1910, I estimate it to be 3200 sq. ft or so. The house appears to have been originally built for two families, at some point the home was split into two rental units, each with their own natural gas boiler. There are huge cast iron radiators on each floor, with smaller diameter piping on the second and third floors. The problem is that the radiators on the third floor barely get warm when the system is calling for heat; the owners have bled the radiators and didn’t get any air from them, so it doesn’t seem to be an air problem. The third floor stays pretty chilly without the radiators functioning, so I offered to troubleshoot their system.

I examined the piping in the basement, the main supply and return lines huge; I would guess 4 inch black iron, there are tees that branch off and go to the radiators with various size pipes. I could see where two 4” lines were terminated by one natural gas boiler and routed to the 2nd boiler. The natural gas boilers are connected to the 4” mains with 1” copper pipe and a single 1/25th hp Grundfos circulator; I don't recall if the circulator was on the supply or return. Each rental unit is one zone with a thermostat on the first floor.

The basement looks like it had a coal bin at some point, based on that, the piping layout, and the size of the chimney thimble I would guess the house originally had a large coal boiler connected to the supply and return lines for each side of the home. There is some sort of vent pipe that has been terminated in the attic, but I couldn’t tell where it originally went. Unfortunetly I did not have a camera with me.

I couldn’t find anything to explain the lack of heat on the third floor, but I wonder if the current circulator and 1” copper piping is large enough to move water throughout the relatively large pipes in the house.

Any advice to further trouble shoot the system is welcome.

MikeyB

gravity

Hey Robert, check out the top banner of this web sites home page and click on "Systems" then click on "Hot Water" than "Gravity Hot water Heating", this should put you in the right direction, Read the sample pages from DAN'S Book. The old vent pipe was probably connected to the old expansion tank

Chris_114

no third floor heat

Without tearing anything up, have you turned the first floor radiators down/off, and waited a couple of days to see the reaction of the system? Was this building split up-down or side to side? The piping from your description sounds iffy, along with the size of the circulator, perhaps the large original pipes might save you. play with it, take your time and observe before you re-do anything, one might find a good balance.

Robert_25

Thanks for the tips, I will read the items suggested.

Chris, since I was only visiting, I will have to call them with instructions for what you suggest. I did not make any adjustments while I was there. The building was split side to side, it has a separate heating system on the left, and another on the right. The first & second floor radiators do get warm, but not nearly as hot as I would expect with the boiler at 160-180F. I actually think the radiators on the second floor were warmer than the ones on the first, but I did not have any instruments to confirm this.