Defective radiator

Bob_121

hi all.
I have a question on my newly installed radiators. They are cast iron radiators purchased from a local plumbing/hardware store.
its about 16 columins and about 2 feet tall.

The unit heats up well and all sections gets hot, but it also cools a lot faster than the smaller radiator.
What can be the cause for this?

Can it be a defective radiator valve that limits the amount of steam into the radiator therefore when the t-stat is satisfied, the unit cools faster due to less steam inside the radiator?

Thanks

Jamie Hall

Unlikely...

to be defective -- there isn't much that can go wrong with a hunk of iron!

If all the sections get hot, it's getting enough steam. However...

How heavy is it in comparison to the 'smaller' one? The heavier it is, the longer it will take to heat up -- and cool down. Occurs to me that it may be a lot lighter.

Big Ed_4

Or

They could have been better designed in convection which would cool them off faster.

Bob_121

Jamie, that is what puzzles me.

the unit is bigger than my smaller rad but cools down ALOT faster....

and why would the design be better if it cools faster? dont we want it to retain heat when the t-stat is satisfied?

Steamhead (in transit)

How about

taking some pics and posting them here, so we can see them?

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Charlie from wmass

My money is on better convection on the taller unit. are you sure they are reaching the same temp? Hot can be 140*F or 220*F. Also the room for the larger unit may have a higher delta T from the rad than the room with the small unit. Do you have the EDR of each unit?

kpc_64

where in...

the room is it? is it on a cooler wall or near windows? If there a high degree of heat transfer it will cool down faster.

Jamie Hall

not necessarily

the retention of heat by a radiator has always been one of the nicer features of cast iron radiators -- whether steam or hydronic. But the objective of the whole exercise is to transfer the heat from the boiler to the room, so one which has better convection may just be doing fine! Big Ed has a good point. So does Steamhead -- some pictures of the old and new might be enlightening.

Bob_121

no problem, i will take pics tonight and post them.

are there any difference b/w hot water heat radiators and steam heat radiators?

the reason i ask is because the tapping for the radiator vent is at the top of the radiator opposite the supply valve.
Dan's book mentioned that the location should be 3/4 of the way down from top.

if this is indeed a hot water radiator? should i leave it in, the unit is getting hot.

scrook_2

or...

thinner radiator walls/less mass? Maybe some of both.

1 psi steam is 1 psi steam... so hot is hot (~214°). If it was hot water w/ restricted flow that would be a different story.

kpc_70

a ha

the vent should be lower, could be part of the problem there should be a tapping there. Hot water rads can do both steam and hot water. TRUE steam rads can only do steam... they are not coneccted accross the top.

Bob_121

my new rads looks like these slenderized ones from burham:
http://www.burnham.com/slenderized_radiators.htm

the picture shows the vent tapping on the top opposite the supply valve.

the attached pdf shows two tappings. Dan's book recommends air vent to be toward middle opposite of supply, what is the used of top vent tapping?

scrook_3

air bleeder...

valve on a Hot Water radiator.

For a steam radiator you'd plug it or wouldn't drill and tap it in the first place, and would put the steam air vent about 1/2 to 2/3rds of the way down, opposite end from the steam main connection