What Can Stop A Radiator From Getting Hot?

FXProglJr

yes Fred...but:
1) shouldn't the vents stay open until the radiator is hot (mine don't), and
2) the very biggest radiator on the first floor is always the very first one that gets up to 195*...So - should I just put a vent with a smaller hole on that one?

Fred

FXProglJr said:

yes Fred...but:
1) shouldn't the vents stay open until the radiator is hot (mine don't), and
2) the very biggest radiator on the first floor is always the very first one that gets up to 195*...So - should I just put a vent with a smaller hole on that one?

Yes to both of your questions. The vent shouldn't close until steam travels across all the raditor sections. keep in mind most vents, even Main vents close at around 130 to 140 degrees so it may not be unusual tht they cloose if that end gets in that range.
If I'm reading your diagram correctly, you have a 1-1/2" main feeding steam to 146 Sq. Ft. of radiator EDR. I think that is pushing the upper limit of a 1-1/2" pipe. I'm sure someone with a sizing chart will chime in with the capacity of a 1-1/2" pipe. I know you have a 1" drip leg at the ends of that main but that actually doesn't do anything in terms of helping reduce the need for return water space in that 1-1/2" pipe because water still has to run down that main from the radiators to the drip legs so the Main still has to be sized for both steam and condensate.

To your second question, yes putting a smaller vent on the large radiator will slow it down.

BobC

The mains table I have only goes down to 2" - 386 edr when condensate and steam flow in the same direction. There is another chart that deals with horizonal runouts where the steam and condensate flow in the same direction and that table rates a 2" pipe at 432 EDR. I really don't know what the difference is.

That second chart rates a 1-1/2" horizontal pipe at 224 EDR IF the condensate and the steam are flowing the same way. Even f we derate that by about 10% (because of the main table that still leaves you with a rating of about 200 EDR. That number will be a lot lower if you don't have proper slope on the main. Check the slope and be sure all the piping is insulated.

Bob

Fred

Thanks @BobC.
It looks like the main is Ok if there is good slope.

Fred

I think I found the problem with that radiator. A 1" suppy pipe can only support a 20 (marginally 30) EDR radiator. I believe the radiator you are currently working on is 50 EDR. It simply is not getting enough steam to heat like it should. Probably just enough to fill a portion of the sections. That radiator should have a 1-1/4" feed to fill properly. I'm guessing it has never worked right or the feed was down-sized when they did the kitchen remodel.

FXProglJr

Actually, rad #1 (the 50 EDR rad) is the first rad to get hot and it gets up to 195* all the time and it's fed with a 1" pipe. Now, we're trying to see why the vents on rad #4 (32 EDR) close before the rad is hot (and the furnace is still making steam). Don't forget that my furnace is pretty over sized (rated for 471 and connected rad EDR of 318) which results in my system cycling on pressure a before the thermostat is satisfied.

BUT - after listening to everyone's comments and studying the layout of my pipes, I think I did find some problem(s):

1) the oldest problem first. I rigged up a water level and checked the last few feet on the main for the first floor (the section where rad 4 is attached). It seems to rise about 1/4" in the last 5 feet. That's because when they changed from coal to oil, the piping for the oil tank interfered with the main - see attached - and they pushed the main up a bit (or the building has settled a bit). Do you think I should rearrange that pipe to make sure it slopes toward the end of the main?, and

2) when they rearranged the kitchen (and rad#4), they just capped the old 1" runout for rad #4 (I've now removed that piece of pipe and plugged the tee) and then inserted another tee at the end of the main between the existing tee and the vent - see attached) for a new runout to the new location of rad #4. (NOTE: earlier, in response to some comments about venting, I removed the single Gorton #1 and put in the antler you see in the photo with 2 Gorton #1's). Does this arrangement need to be rearranged to put the runout for rad#4 before the vent?

Captain Who

A vent can close due to steam hitting it and there could still be trapped air in the radiator, conceivably. It is not normal, definitely. Is there a possibility that the radiator(s) in question were at one time used as hot water radiators and are all scaled up inside? If so, perhaps you could determine that with one of those endoscopic cameras, or you could just remove the radiator, descale it and put it back in service to see what happens. It would be interesting to look at your various radiators with a Flir (sp?) video camera as they heat up and record the video to see the differences between the ones that are heating properly and not.

Sorry, just some quick thoughts. Pretty busy.

Fred

I think the vent arrangement is probably Ok. That Main that is pitched up to accommodate the oil tank piping will definitely cause that Main to hold some water, at that end, very possible enough to cause the steam to condense on its way to the radiator. See if you can get the pitched the right direction.

FXProglJr

Captain Who - thanks for the thoughts...if I can borrow a FLIR camera from my friend again, I'll take some pictures as the rads heat up and post them. As for the possibility of scaling, that'll have to wait until the spring (or until I can get another rad to put in its place)

Fred - if the existing main vent arrangement is ok, I'll need to figure some pipe arrangement that will allow me to drop the main 1/2" or more without screwing up the pitch on the return. That's take some thought and it'll also have to wait for a bit warmer weather. I'll let you know how I make out.

Many thanks to all for your help.

Frank

FXProglJr

Well....I was down in the basement again looking at the main in question and remembered that I had removed the old runout that was capped just below the floor and left when they moved the location of rad#4 and I had plugged the opening in the tee. So - I waited for the furnace to be off and pressure to drop, removed the plug and got on a ladder with a flashlight to look down the hole. Sure enough, there was about 1/4"-3/8" of water laying in the bottom of the main as far as I could see up and down the main and it wasn't flowing in either direction. I guess we've found the (or another) problem. I'll get to that as soon as I can and report back.

But, then I was thinking (again - just trying to understand what's happening). If everything was sloped properly and condensate was returning, wouldn't there be water in the main anyway? And why is this water different?

Fred

There should not be any water sitting idle in the Main, especially a 1-1/2" pipe . The Main may be wet on the interior walls but no standing water if propery pitched.