gravity hot water

kevin_58

I have a customer with a pressurized gravity hot water system no circulator. Boiler is from 50's. The original cast rads heat fine, there is 1 section of 3/4 baseboard that does not. Can baseboard work in a gravity system. The pipes are reduced to 3/4 and run 10' to baseboard. I tried to blead but no luck. ther are old crusty valves in basement. I was going to shut supply blead then open shut return blead then open but the valves are in bad shape and did not want to try because im not sure if baseboard will work in this system with smaller piping.

Steamhead

Nope

the pipes and baseboard have far too much resistance for gravity to work. Adding a pump won't help, the water will still go where it meets the least resistance. De-knucklehead that system with a proper radiator and proper piping. 

Mark Eatherton

It CAN be made to work, but....

the occupants will NEVER be comfortable.



Baseboard is 90% convective (air heating) and less than 10% radiant. The radiators, on the other hand are mostly radiant and less convective (have heard 60/40).



The net effect is that when you walk into a room that had a radiator in operation, you CAN feel the difference, because the radiator has significantly affected the Mean Radiant Temperature (MRT). If you look at an air sensing thermometer, it will probably say 70 degrees F, but if you could look at the MRT, you would see a higher number.



When you walk into a room in the same home that is heated with baseboard, the thermometer will still say 70 degrees F, but your body will NOT feel like it is 70 degrees F, due to the lower MRT. And the consumer will NOT be happy in that room, and won't be until you raise the MRT to match the other rooms loaded with the heavy cast iron radiation.



Making it work is going to require a lot more money than it is worth (pumps, re-piping, check valves, controls etc) so I concur with Frank. Increase the pipe diameter and put a good ol' upright cast iron radiator in. If they won't give up the space consumed by the radiator, then the trade off is comfort. If money is not an issue, install some good looking Euro radiators, with TRV's. increase their comfort levels, and reduce their cost of operation, and recover space consumed by the upright cast iron radiators. Or, switch them to a large surface radiator (walls, ceilings and or floors) and deliver great comfort.





My two cents worth...



Keep the change :-)



ME



Tough call, but if you educate the consumer, they might follow your lead.



ME

kevin_58

gravity system

Thank you for the responce. I didnt think it would work but was not sure.

JIMBO_2

How about CI baseboard?

I understand what you are saying, but I encounter many homes with CI rads AND CI baseboard.  And they seem to work fairly well.  Would a stand up rad be a better emitter in a system originally designed for radiators (usually a converted gravity system often combined to a newly installed boiler of 85 to 90 %).