Convectors replaced with smaller cast rads?

guzzinerd

Previous building owner threw out 5 of the buildings 26 old (steam) 1930s cast convectors and replaced them with cheap baseboard units.

I'd like to replace the baseboard units with real rads.  Can I consider smaller traditional cast rads or will I need to stick to the original style combination cast & copper models?  

Thanks 

mattmia2

You need to figure out your heat loss which will then tell you how much heat they need to output. From there you can figure out what emitters will output the heat you need. Is this zoned separately? If the building is all one zone you need to consider balancing it with the rest of the building too.

guzzinerd

It's all one zone.  The boiler cycles a couple/few times at 1.5psi by the pressuretrol before it gets to temp so the capacity is there

Thanks

mattmia2

That just says that the boiler is producing more steam than the emitters can consume, it says nothing about if they are producing enough heat or too much heat.

Since it is all one zone you will want the amount oversized your new emitters are matched to how oversized the other emitters are so that when the system shuts down because the building is hot enough from those other emitters your space is also hot enough. Some balancing can be done by changing venting.(I assume this is 1 pipe steam). If the mass of your emitters is very different from the other emitters that will also present a balancing problem.

guzzinerd

It's a 2 pipe system.  I'd be replacing the missing original units with the same size(BTU) emitters that were removed.  It helps that we still have most of the original rads in the other units in same-sized rooms as a reference.

The problem I have now is that the new cheap baseboard emitters put out way less heat than the originals.  The 3 units that have all the original convectors are noticably warmer than those with the new cheap baseboards.  Just trying to even it all out so everyone is cozy.

mattmia2

A convector cabinet has a lot more output than a piece of fin tube baseboard. the convector cabinet pulls a lot more air through the element and thee element has a lot more surface area per length of element. you can get new convector cabinets to replace them too. You would use the radiator valve or an orifice plate in the inlet to balance a 2 pipe system.

The mass is probably less of an issue with a convector.

guzzinerd

Exactly.  The mass was reduced when they removed the old convectors and installed the baseboard tubes.

I'm looking at putting the mass back where it was originally (I'll be using radiator valves).  

Mostly wanted to know if a standard cast rad was an option and answered my own questions.

Thanks 

mattmia2

If you go with cast iron radiators I would put TRVs on them so you can keep them from overheating the space.

guzzinerd

mattmia2 said:

If you go with cast iron radiators I would put TRVs on them so you can keep them from overheating the space.

Will do, I think that'll be nice option since the units don't have individual thermostats.