I have received conflicting answers to this question I hope someone can help. I want to add a cast iron radiator to a room which doesn’t have one. I want to know if I can connect to an existing radiator in the next room or do I have to run off the main steam line. Some say I can while others say no. I have a single line steam system .
It is highly probable that the steam will go quickly to the new radiator and the condensate will have to pass through the steam flow in opposition to the steam. This would increase the probability of banging radiation. It is best not to burden the first radiator with the added condensate from a new one on the opposite side of the radiator from the steam source. The runout for one radiator is usually sized to the steam need of the individual radiator, not two. Also, the new radiator would have to be higher by one inch per 10 feet to help the condensate back to the first radiator, which in turn would have to pass the condensate of the new radiator in addition to its own. In short, take the new radiator off the main.