Why is my hot water baseboard heater not heating?

Question

I have classic cast iron radiators in my house and then one "modern" one pictured below. It was installed in the 80s from what I know. It doesn't seem to produce much heat at all.

It is properly bled and the incoming pipe is hot but the outgoing pipe is only slightly warm. The radiator itself is only a bit warm on the incoming side.

BTW, it is on the second floor of the house where I also have a cast iron radiator which works great, so it's probably not a matter of water pressure or anything like that.

I'm not familiar with these radiators, are they not supposed to be hot when you touch them? Or is something wrong with this particular one? What could be wrong?

Should I change it with something better? What? A modern radiator? Used cast iron one? What would you do?

(Edit: changed the title, because these seem to be called 'hot water baseboard heters')

Answer 1

I think the key to the problem you're having is found in the following paragraph from the article that you linked to in your answer:

In systems where the same thermostat controls cast-iron radiators and baseboard convectors, consumers are typically unhappy with the comfort from baseboards as compared with radiators, due mostly to the difference in their influence on mean radiant temperature. When your body is in a room with a mean radiant temperature closer to your skin’s surface, you feel warmer. When you leave that room and go into a room with a lower mean radiant temperature, your body immediately registers the difference. Thermometers in both rooms may show an air temperature of 70°F, but if the mean radiant temperature is substantially less in one of the rooms, your body senses this difference, and your skin feels cool.

Your baseboard and radiators are all connected to hot water loops. You most likely have more then one loop in your house. Each loop will be controlled by a thermostat located in a common area to all the radiators on the loop. Your baseboard is most likely on a loop with other radiators and as such the issue described above is occurring.

If the above is the case, you're probably best to change the baseboard to a similar radiator to match what you already have throughout your house.

Answer 2

I read this article about the differences b/n baseboard and radiator and it seems to me that there are two issues:

1) The perception that you get from the two heating bodies is different, the cast iron radiators just give a sense of warmth.

2) The radiators are radiating heat long after the furnace is off unlike the baseboard heater.

In addition to that the window on top of that heater still has a window AC unit left from the summer which works against the heater.

My conclusion is that I'll remove the AC unit immediately but also I'm thinking whether changing the water heater to a cast iron radiator might be a good long term investment.

Answer 3

You might have a couple of things going on here. Is every radiator on the second floor on the same zone (controlled by one thermostat)? Is this system forced or gravity fed?

For forced hot water you might have a problem with the flow. Quite often to keep the water temperature consistent in each radiator they put a venturi "t" fitting at each radiator location. If the run up to the baseboard becomes too long up to the radiator, or the "t" is not the correct type, the baseboard will not get the water it needs.

My old house had this type of setup where the baseboards were tapped into a 1" cast iron pipe in the basement. There were "t" fittings that went into each room's baseboard and most of the runs were insanely long so the water never made it. Some of the baseboards would feel warm but never hot. The water looped around and around in the 1" pipe in the basement. I had the baseboards linked together one after the other. The drawback to that method is that the last radiator in the series will not have as much heat as the first. It flows so fast and the apartment is small enough that it does not matter.

The water should be flowing fast and hot enough that you can't touch the copper pipe at each end of the baseboard. I can also feel the water flowing through the pipe.

A professional should be able to properly diagnose this.