Venting an elevated basement rad - 2-pipe (Thermal System) - with elevated return main.

ThermalJake

About 10 years ago I was updating my Thermal system and I took this basement radiator (which had been hooked up to the boiler water without even a circulator) and raised it up on some pedestals to get it above the water-line so it would work on steam. I piped it using an abandoned take-off from an overhead supply main and then piped the return from the radiator AND the return from the down-feed riser into the wet return since it is located right near the boiler.

I am the homeowner, but a little less than completely useless. Over the years, I re-installed the burnham boiler that was originally installed with copper pipe and a bull-head tee, and it had no hartford loop. I used 6-inch for the header. A couple of years later, it developed a hole at the water line on the interior, so I replaced it with a MegaSteam 513. I repiped it with a drop-header. I have insulated, and added vents at the end of the supply mains, and updated the one at the end of the return main. And this year, I had the chimney lined. I have moved radiators on the second floor because my wife took out a wall on the first floor that had pipes in it. And lastly, I also raised this radiator up off the floor to get it to work properly.

Since day 1, it would not vent properly. When I put the vent in the top spot, it would close when the temp reached it, and only the top half of the rad would heat. If I put it in the lower spot, it would heat all the way across, but the vent would never close, no matter how hot. This system runs on a cut out of 8oz/in2, so I wonder if that lower pressure keeps the cheapo vents from closing. Finally, I put a manual vent in with a key. I set it via trial and error and left it that way for years. I guess I was fortunate that it heated across enough when the call for heat was light, and it probably lost steam and water when the call for heat was heavy. But it worked well enough.

Now, I'm trying to actually fix it. Ha. So I think that i have three options and I'd like to know what you think:

1. I tried this contraption to see if I could get the vent further away from the radiator before it closed, but also to see if one of those adjustable ones would close on temp. It basically jingled with a little bit of hammer, right at the venturi crated by the 1/8 nipple where it comes out of the rad. And it never closed. So I took off the extended piping and just put the vent right into the radiator for now, while I try a few other things.
2. Some other scheme to vent it, perhaps off of the return elbow. I could make that into a return tee, and run a larger pipe up to a bigger vent, maybe.
3. I could pipe the return up to tie into the return main for the rest of that leg. I could keep the drip leg into the wet-return, but at least the venting would be done through the central return vent back near the boiler and would be connected with everything else.

With both 2 and 3, above, the water line at rest is just a few inches below that return elbow. So under 8oz of pressure, it comes up, but not as much as it would under a half-pound, or anything like that. Perhaps I should consider raising it even higher from the waterline, and then piping the return back into the return main. If I did this I could easily throttle the supply valve to balance it, just like I already do with the rest of the house (this is an orifice system, no traps.)

Anyway, whattyou think?

ThermalJake

Steamhead

I've seen these setups work, and you do NOT need a vent on the radiator. 2 questions:

1- how far is the bottom of the radiator above the boiler's waterline?

2- did you pipe the radiator's outlet up to the dry return as well as the wet return?

ThermalJake

Hey, Steamhead. It's been a while;  I hope you are well. 

The water line, at rest, is right at the return elbow... just at the bottom of the radiator. So under pressure, its probably swamped at least a little bit. 

I did not pipe the return up and into the dry return. 

Thanks. 

Jake. 

ThermalJake

There is a place that I can remove a plug and tie in to the dry return, but I'm concerned about two things: 

1. I dont want pressure in the dry returns from this radiator to affect the pressure differential from the other radiators. So I'll just have to balance the supply valve accordingly. That should be no problem. 

2. I think I need to raise this radiator a little bit higher above the waterline so that the return doesnt have to go through a water seal. 

ThermalJake

I took off that other gizmo and out the variable vent right on the radiator, like this pic. The upper one closed, but the lower one is just hissing away. 

And I assume that if the water line is above the nipples between the sections, then that's why it is only getting hit across the top, rather than halfway down each section. 

Steamhead

ThermalJake said:

There is a place that I can remove a plug and tie in to the dry return, but I'm concerned about two things: 

1. I dont want pressure in the dry returns from this radiator to affect the pressure differential from the other radiators. So I'll just have to balance the supply valve accordingly. That should be no problem. 

2. I think I need to raise this radiator a little bit higher above the waterline so that the return doesnt have to go through a water seal. 

Right on both counts. "B" dimension!

ThermalJake said:

I took off that other gizmo and out the variable vent right on the radiator, like this pic. The upper one closed, but the lower one is just hissing away. 

And I assume that if the water line is above the nipples between the sections, then that's why it is only getting hit across the top, rather than halfway down each section. 

Exactly.

ThermalJake

Sorry. I got spam blocked because I tried to post the pic right away. Ha. 

EBEBRATT-Ed

need to raise it it's waterlogged. That's why they put basement radiators on the ceiling sometimes.

Dave in QCA

When I look at your setup it makes me think about how they usually piped an indirect radiator on a 2-pipe system. They would mount it near the ceiling, but because of the bulky dimension of the indirect, it was usually not possible for it to be above the steam and return piping. What they would do is pipe the steam into the supply. (of course) They didn't worry much about dripping that supply line, they just let it drip into the indirect radiator. At the bottom of the indirect, they would connect a drip line that would run down below the water line before connection to wet return piping running to the boiler. At the vent port, they would run 1/8 piping to a Paul type vent, or a Dunham Air Service vent trap. Hoffman Model 3, is still available for this purpose. The outlet from this air trap would be connected into the dry returns. I guess there's really no reason you couldn't use a 1-pipe type vent as long as you are not trying to hold vacuum during your off cycles. As has been mentioned by others, the critical measurement in this type of installation is for the bottom of the radiator to be above the B dimension. In Dunham Handbook #414, they specify that the bottom of an indirect radiator be "at least 24" above the water line, more if possible". This setup would let you orifice the inlet and get it operating like all the other rads in your system.