Boiler won't work on cast iron radiators?

From everything that I've ever read on this site.....Cast Iron radiators are 'da bomb. They radiate more heat than b/b with the same feed temp. I don't get it either.

np

These only work incorrectly -- if installed incorrectly!

the old cast iron radiators are probably originally designed for steam. We had a plumber friend of our retrofit ours for hot water and they have been working great. Honestly all I think he did was change the fittings that went into them and added a valve on each one so we could shut down if we ran into trouble wihtou draining the whole loop. I have 5 of them in my basement on a zone as a heat dump in case the boiler overheats or I can use it to heat the basement but the pipes and boiler take care of that for me.

From the quote you have listed I don't see that it won't work with cast iron radiators. Works best with baseboard doesn't seem to indicate it won't work at all or decent with CI radiators. As Huskurdu says CI radiators are da bomb, Randy

I can't recall exactly but there is a difference between hot water and steam radiators. Looking at the steam units they have an extra pipe running horizontally or something. But, I also recall that you can retro fit steam to hot water. You should look into this because of the added expense of conversion if necessary.
The do heat nice regardless.

im converting steam rads into water as we speak...
easy actually, remove the union and other plug on the other side....replace with black pipe, pressure test....BAM!
well. IF you can get the dang bolts out!!

There are CI rads that can be used for either hot water or steam, and ones that are intended for steam only. The difference is whether there is a passage at the top of the rad connecting all the columns. A rad that has the top passage can "easily" be converted from one to the other by changing fittings (which can be a challenge as noted) The rads without the top passage are nominally for steam only, and won't work well with hot water unless special approaches are used.

The problem with the steam only rad is that you can't readily bleed the air out of them, so there is no easy way to get the water into them and you end up just heating the bottom couple of inches as the water flows along the bottom - obviously not a good thing.

Eric says that he is using a smallish steam only rad in his hot water system, but he had to disconnect it, put a shutoff valve on each fitting, turn it upside down, fill it with water and close the valves, then reconnect it, etc... He has a hot water rad immediately upstream from the steamer that acts as an air trap, or he would be needing to do this on a regular basis to keep it from airlocking. Given the weight of a rad, especially if it's full of water, this is a non-trivial excersize, and is why most people would probably say it can't be done... Eric had a whole thread on the care and feeding of CI rads, it is worth the read.

Don't know if the issue with the system mentioned in the OP was because the person had steam-only rads, or if there were some other issues, but thought I should mention it.

Gooserider

i believe mine are both steam and water. plugs on the tops as the bottoms...
an thread with pics to show...


https://www.hearth.com/econtent/index.php/forums/viewreply/372889/

88rxn/a said:

i believe mine are both steam and water. plugs on the tops as the bottoms...
an thread with pics to show...


https://www.hearth.com/econtent/index.php/forums/viewreply/372889/

Click to expand...

Yes, those definitely look like the steam / hotwater type... And unless I'm badly off base, I think that's the big CI rad thread that I mentioned in my previous as well...

Gooserider

You can easily tell if the rads are sshhteam only. The columns are not connected at the top at all. A rad that is usable for hot water will have an upper set of tappings as well as having all the columns connected on top. Some may have a small 1/8" tapping for an air vent in one of the plugs on the end.

If someone _really_ wanted to use the steam-only type (not connected at the tops) with hot water, and wasn't phased by doing some extra work and having it look a bit unorthodox you could probably drill and tap for a set of vent/bleed plugs at or near the top (maybe the back top) of each "bay."

Gooserider said:

88rxn/a said:

i believe mine are both steam and water. plugs on the tops as the bottoms...
an thread with pics to show...


https://www.hearth.com/econtent/index.php/forums/viewreply/372889/

Click to expand...

Yes, those definitely look like the steam / hotwater type... And unless I'm badly off base, I think that's the big CI rad thread that I mentioned in my previous as well...

Gooserider

Click to expand...

yep, and a great thread it is!