Big **** vent

NealJ

I’ve decided that the most likely problem with one of our problem radiators is lack of adequate venting (surprise, surprise). It rarely gets any heat, at most the first few tubes on the steam end. Vent was replaced, but looking at the piping configuration, this is a separate main. It comes off the boiler header separately from the house main. This ‘secondary’ main goes across two basement rooms (with one basement ceiling convector) then goes up the equivalent of 3 stories before hitting the problem radiator. There is no vent in this piping, only the radiator vent. Measuring the 1-1/2” (and a little bit of 4”) pipe, I get 1.42 cubic feet of pipe, plus about .8 cubic feet for the large radiator gives me a total of 2.22 cubic feet to vent. Divided by 3 minutes and I need .74 CFM to vent it in 3 minutes. I’m nowhere near close. The question is: I have a 1/8” NPT tap for the vent. Has anyone drilled and tapped the vent connection larger? Recommendations for a vent?

Waher

A 1/8" NPT Heat Timer Varivalve Max Setting Angle Pattern is 0.850 CFM @ 2oz. of pressure allegedly, which should get you in the ballpark of what you think you need.

Long Beach Ed

I often drill and tap a radiator for a second vent. Most radiators have a second boss that can be drilled. Beware that too much venting can give you other problems.

NealJ

Long Beach Ed said:

I often drill and tap a radiator for a second vent. Most radiators have a second boss that can be drilled. Beware that too much venting can give you other problems.

Thanks Ed. I’ve read some of the warnings. The lucky part is that it all can be undone. According to people that have been there for a long time, this radiator has never worked. They even had an electrician run two new 20 amp circuits to the room (it’s a meeting room) so they could safely put in a couple of electric heaters. This is a long run of pipe from the boiler header (58’ of mostly 1-1/2” pipe with nothing at the end but this radiator. I’m excited to give it a shot!

Long Beach Ed

You can see how a second vent would work by simply removing the one and firing up the boiler. If it solves the problem, drill the radiator and install the second.

Make sure you check for any sags in that long runout and make sure the radiator valve's not stuck closed. Insulating this pipe (if it's not) will help too.

Another solution would be to put a main vent on the end of that radiator runout or riser before the radiator valve. We replace the angle valve with a reducing tee. On the top of the tee we put a nipple and main vent. On the bull of the tee goes a straight valve and the radiator. The one shown below is on a radiator in a situation similar to yours.

As an option or a final effort if this radiator still doesn't heat, you slow the venting on the others. That will allow steam to find its way to this cold radiator as the lowest pressure point.

At a cost -- you can make this the hottest radiator in the place.

ethicalpaul

If it doesn't help then you'll have to look for a low spot in the supply piping that is holding water.

NealJ

Waher said:

A 1/8" NPT Heat Timer Varivalve Max Setting Angle Pattern is 0.850 CFM @ 2oz. of pressure allegedly, which should get you in the ballpark of what you think you need.

I ordered one today. It is certainly reasonably priced compared to other large vents. Today I ran the system with the vent removed (3/8” NPT, which is about a 1/2” hole with vent removed). Once heat got to the radiator, it still took about 10 minutes to get from one end of the radiator to the other. I’m not sure how the Verivalve can vent that full capacity via a 3/8” NPT connection (3/8” ID). It will certainly be an improvement over the tiny vent that existed.

Danny Scully

If the rad didn’t heat quickly with the vent removed, I’m sad to tell you it will heat even slower with the varivent installed. Have you clocked the meter to confirm the firing rate?  

pedmec

As always with steam the issue is very rarely at the place your having a problem. Most problems start at the boiler but cause issue outside the boiler room. check and make sure your boiler is operating correctly. Clock the gas meter as Danny Scully has pointed out make sure getting the rated output. check for short cycling. You could have an unstable water line tripping out the low water cutoff. Plenty of simple causes for the radiator to not heat.

NealJ

Danny Scully said:

If the rad didn’t heat quickly with the vent removed, I’m sad to tell you it will heat even slower with the varivent installed. Have you clocked the meter to confirm the firing rate?  

I understand this, but it will help a lot compared to the very small Hoffman #40 that was there. I’ve got most of the rest of the system up & running well, no short cycling. This one radiator is on its own main, and farthest from the boiler. This main has no main vent, and no provision for one. It vents through the radiator. I may drill and tap for a second vent because I really don’t have a place to install a vent at the top of the vertical main (3rd floor radiator). According to the old timers there, it has never put out any heat. My calcs showed 0.74 cfm to vent the piping and the radiator in 3 minutes. It’s not there yet. Not sure what it means to ‘clock the meter to confirm the firing rate” means. Is this the gas to the boiler? In this case, the boiler and near boiler piping are fine and the rest of the system is (mostly) running well.

Long Beach Ed

Vent the riser to the radiator and slow down the venting on the other radiators.

EBEBRATT-Ed

Try two vents on the rad first. If that doesn't work vent the riser

Danny Scully

@NealJ, I’m assuming you sized all the rad vents based on rad/runout cubic feet of air and the main vents based on cubic feet of air as well? With clocking the boiler, it’s important to see it’s firing the rated BTUs, again assuming here it’s sized right. I had a job nearly identical to yours, and after some improvements with insulated the long 1-1/2 runout, adding a master vent and a large rad vent, I still wasn’t satisfied with the timing. I sat, listened and watched the boiler fire. It was a step opening gas valve but barely opened any more on its second step. I clocked the meter and lo and behold it wasn’t firing at its rating. I adjusted the gas valve and, no joke, in seconds that rad got hot completely. 

BobC

Clocking a gas meter is done to make sure an appliance is burning the right amount of gas -

• Look for the smallest test dial on the meter. Get a stop watch. Get the single piece of equipment you want to clock running. Everything else should be shut off, don't worry about pilots on other equipment. If for instance the test dial you are using is the 1/2 foot dial let it make two rotations (makes the math easier) It becomes the same as a 1 foot dial. So lets say it took 20 seconds to make two rotations of the half foot dial. You divide 20 into 3600 (number of seconds in and hour). In this case 20 divided into 3600 is 180, what is 180 it is 180 cubic feet to then find BTU's multiply 180 times the Heat Value of a cubic foot of gas in your area or if you don't know use 1,000 which means the equipment you clocked is burning 180,000 BTU's per hour. This should closely match what is on the rating plate of the equipment listed as INPUT.

There are charts and tables for all of this in NFPA 54 National Fuel Gas Code. There is also a procedure for altitudes in NFPA 54.