Cold radiator

queenanne

Need help solving a riddle re: a cold radiator. 1896 Queen Anne Victorian. New gas boiler in 1996... hot water radiators... 9 on 1st floor, 6 on 2nd floor... piping is mostly cast iron with a few copper runs. We moved in 1991. Radiator system has always worked very well, first with original oil burner and with gas boiler. In 2003, we removed a radiator from the kitchen for renovations and capped off the pipes in the basement. 2 years ago, we reinstalled same radiator in a new location about 10 ft away from its original spot. We verified good water flow with no leaks before reinstalling, bottom in, bottom out elbows go through baseboard then drop down to pex connection ( not enough room under floor to go straight down). Plumbed into same capped pipe but ran HePex instead of making all the funky turns with copper, no shut off valve at the radiator). Upon reinstallation, we refilled the system and fired up the boiler. Radiator heated right up, but within hours was cold. We have been unable to get it to heat up since. All other radiators in the house work fine, as they always have. We have bled all radiators ad-nauseum, bleeding produces cold water out of this radiator, we have let gallons and gallons run through it while re-filling the system, we have cranked the heat to the max, we have shut off other radiators where possible ( not all of them have valves), we added a riser to the connection nearest the furnace. Once the system is heating, the inlet pex tube remains cold but the return feels warm. FIL used to repair boilers in the 50's and 60's and he's stumped. What else can we try??

Steamhead

The fittings in PEX restrict the flow of water. This probably was a gravity system originally, with no pump, so the pipes were larger to keep the resistance low. Even if the installer used the same size PEX, it will resist the flow of water more than the original piping.

Repipe it with copper and make sure the new piping is the same size as the original. Make sure the pipe slopes up toward the radiator so air cannot collect in it. I bet it works great once that's done.

queenanne

We were hoping to somehow make the Pex work but we are getting so frustrated that we had this very same idea earlier today but were reluctant to do that only to have it not work. I have more confidence in this plan now ! Thanks!

queenanne

It worked!!! Thank you so much for your help!

Steamhead

Glad to help.