thanksgiving is a great day for vapor discussions!. i put in a megasteam about 8 years ago for a customer who has since moved to a new house. there were a few problems with the existing boiler ( and system) but once it starting leaking all over the floor he finally decided to buy the new machine. anyway, one or 2 problems never went away and i was called there yesterday by the new homeowner to revisit these issues that they thought were new. so in a nutshell, there are 2 radiators in that dont heat. like ever. these are the only 2 radiators in the entire house where the steam is supplied to the bottom of the radiator through regular hot water style modern radiator valves. the condensate returns of the radiators are just 3/4 elbows. no orifices. the vaporstat is set to 6oz with a 4 oz subtractive differential. heat everywhere else is perfect. the suspicion is that the kitchen was added onto and these are not the original radiators. i believe they were replaced years ago since all the piping to them has teflon and they are shorter than all other radiators in the house. most likely to fit under the windows. so in an effort to get these radiators th heat i have a few options and not sure which is best. 1. pipe the steam supply to the top and leave the condensate where it is. this will match the other radiators in the house but will still have a regular radiator valve. not sure is a calibrated vapor valve is still available. (im sure i can calculate an orifice and stick that in the union... ) 2. what if i remove the return elbow and replace it with a steam trap? with that work? 3. what if i remove the condensate return entirely, pitch the radiator the other way and add a radiator steam vent essentially making it a 1 pipe radiator? 4. something i havent thought of? I also have a few questions with the main venting. currently the steam leaves the boiler in 3" for 15' and them splits to 2 2" mains. i main is 45' and the other is 25. these mains come back to the boiler and have vents on them before they drop into the hartford loop. the condensate returns follow the mains around the house and tie together in the ceiling before they also drop into the hartford loop and there is a main vent on this pipe also. no f&t or any other traps in the system. so are these vents correct in placement? should i take the ones off the mains and put a huge one on the condensate return only? should the condensate return not have one at all? the pics im sending are not great and dont criticize me on the insulation. it was the homeowner. but at least he tried!! 1st pic is of common to all the radiators in the house except for the 2 not working. 2nd pic is the 2 not working. 3rd is a pic of the main vents. the 2" is the main and the 1-1/4 is the condensate return. there is another 2" main not pictured which also has a vent. other pics are just for clarity.