Third floor is cold

foresthillsjd

I installed a vapor stat and have it set at 8 oz main with 4 oz diff, and now my third floor is cold.  

The main venting seems to be okay, and I put the fastest radiator vent I could find on those radiators.  

So should I tap a hole for an additional vent on the radiator?  The riser leading to the vent is covered by a soffit.  To access it, I’d have to cut open the inside of my daughter’s closet.  I would do it if a vent there was appreciably better than one on the radiator.  What are your thoughts?  Offending radiator here. 

Also, any tips for drilling the hole?  Go slow?  Push hard?  Cutting oil?

mattmia2

Are there other radiators off the section of main these are on? where are they in relation to the radiators that are heating? Do they heat if you turn the t-stat up a few degrees so it runs a long cycle?

Dud they heat at higher pressure? that usually mean air wasn't being vented but was being compressed if it heated at higher pressure.

Hap_Hazzard

Do you have a feel for how frequently the heating cycles run? If the boiler is cycling on pressure, there would be multiple stop-start cycles in each heating cycle, but I'm interested in the whole cycle, from when the thermostat initially calls for heat until it turns it off because the set temperature has been reached.

Also, what kind of thermostat do you have? (Post a picture if you're not sure.)

Let's get a handle on this before we go drilling holes.

JUGHNE

Your air vent is too high for steam.
That is the location for hot water heat air venting.

Steam air vents are usually in the lower 1/2 of the radiator.
Look at your other radiators that work OK.

The steam comes up to the top and shoots across the top connected section and closes the vent early. More pressure would have forced more steam into the rad.

Look on that rad there might be a lower port with a plug or a "boss" flat where it could be easily drilled and tapped.
Or show us the vent end of the rad.

foresthillsjd

Hap_Hazzard said:

Do you have a feel for how frequently the heating cycles run? If the boiler is cycling on pressure, there would be multiple stop-start cycles in each heating cycle, but I'm interested in the whole cycle, from when the thermostat initially calls for heat until it turns it off because the set temperature has been reached.

It takes 20-25 minutes for the radiators on the second and first floor to fill all way across and the third floor radiators stay cold. Then the system cuts off on pressure. It hasn't been really cold yet, but right now in NY, I think? it only takes one cycle to get the temp up the degree it needs.

Also, what kind of thermostat do you have? (Post a picture if you're not sure.)

I have a Google Nest, one that's about a year old.

foresthillsjd

@JUGHNE

mattmia2

That small plug about 6" up from the bottom with the allen head is for the steam vent.

JUGHNE

Yes, that would be the place.
Being an Allen plug means it is not 80 years old and might be unscrewed.
Need to clean paint out of Allen hole and around the threads, I use a right angle dental pick for that.
Then a little PB blaster or such to soak the threads several times, caution for your new paint.

A few taps with a hammer straight on, then with a good wrench fully inserted you might try just a bit of tightening and then unscrewing.
You just do not want the Allen flats to strip out or then it is drill time.

ChrisJ

The Nest isn't great and the vent isn't in the best spot but that's certainly not the main issue.

All of the radiators should be getting hot at fairly close to the same time. If I was you I'd start by slowing the venting on the 1st and 2nd floors. Something like a Gorton #5 and use Gorton #6's on the third floor. If there's still a large gap, then drop the faster ones to Gorton #4's and the slower ones maybe raise them to Gorton C's......but I wouldn't do it all at once.

Speeding up radiators will slow others in the system down etc. They all effect each other, it's a network that needs to all cooperate.

mattmia2

Get the socket type of allen bit that goes in a ratchet and push in hard on the socket from behind the wrench while you try to turn it so it doesn't cam out. Use a pipe on the wrench handle of you can't easily turn it while pushing in. Don't use a bent hex shaft type allen wrench, it is a lot easier for that to cam out and strip it.

If it is a vent location problem, the supply pipe and the top of the radiator and the vent will be hot while the boiler is on.

Steam needs to run relatively long cycles, A nest isn't always great at making sure that happens.

cross_skier

These guys are 100% correct on location of radiator vent.   If that doesn't completely solve the biggest 1/8" Gorton vent on the riser will work.

Mains and risers should be vented fast, radiators are vented more slowly.

ethicalpaul

After you get the venting squared away, I recall that you replaced all your old radiators with these new ones. Were they sized for the heat loss of the rooms they are serving?

foresthillsjd

@ChrisJ I have Maid O Mist #4s on all the first and second floor radiators, so I think they are as slow as they can get. Is there anything slower?

@Mattmia2 I agree that ideally, they should run long cycles, but my boiler is oversized for the radiation, and the house is really well insulated, so once the boiler starts firing, it goes up 1 degree in under half an hour, on one cycle.

@ethicalpaul very good memory! I went from 80,000 to 70,000 (counting just radiators) and I balanced it a bit more between rooms. (Even though the heat loss was calculated to be 40,000 btuh for the whole house, I tried to keep the radiators proportional to the heat loss calculation) The bulk of the reduction was just on three radiators, two on the first floor and one in a tiny room on the second floor that was always too hot.


So I tried it with two vents and it’s much better, but still not getting hot all the way across the top of the radiator before the system shuts off on pressure. Would it actually be better with one vent, just in the bottom?

The first and second floors are perfectly balanced between rooms, but all my experiments have made it 77 degrees down there while it’s 65 on the third floor.

mattmia2

foresthillsjd said:

So I tried it with two vents and it’s much better, but still not getting hot all the way across the top of the radiator before the system shuts off on pressure. Would it actually be better with one vent, just in the bottom?

Ok, now we're getting somewhere. So it is heating, just not all/most of the way.

Yes, moving the vent to the bottom will make it heat more. What happens when the vent is at the top is that the steam that is lighter than air goes to the top of the radiator and move across between the sections at the top and to the vent and heats the vent and closes it while most of the raditor is filled with air trapped there by the steam.

If the vent is near the bottom the steam moves across the top and pushes the air down and out the vent until it fills with steam down to the level of the vent.

Are any of the vents you are trying now at the bottom?

You may need to put slower vents in the radiators near the thermostat so those don't heat as quickly.

ratio

If you aren't able to get to the top of the riser to vent it, that radiator vent is doing a lot of work. Maybe leave that one, to help vent the riser quickly, and add one at the lower boss to vent the radiator itself. You'll have fast venting from both vents to help get the steam upstairs and then once the upper one closes the venting will slow down so condensate can easily return, but we'll still be able to fill the radiator.

ChrisJ

Don't go slower than the #4s, go faster on the third floor.  You can vent the piping separate from the radiators.

cross_skier

I would be leary of too big vents on 3rd floor radiators.  Those vents will likely close b4 all sections of radiator are hot.

Better idea to to put bigger vents on top of risers and modest size vents on radiators.

JUGHNE

foresthillsjd said:

I installed a vapor stat and have it set at 8 oz main with 4 oz diff, and now my third floor is cold.  

You have dropped the operating pressure and perhaps run shorter cycles?
How did that heat without the vapor stat?

My guess is that the higher pressure of maybe 1 1/2 PSI might have pushed more air out with the longer cycle. You may of had 3 X the pressure you have now.

That is a good idea to leave the existing vent in place and add a second at the lower port.

EBEBRATT-Ed

If the rad on the third floor is not banging. I would try leaving both vents on and increasing the vent size. If that doesn't work vent the riser.

Maybe a vent on the riser even in the basement might speed things up

Jamie Hall

I myself have come increasingly to believe in riser venting, especially for one pipe systems. We've always placed a lot of emphasis -- quite correctly -- on main venting, but, when one thinks about it, what is a riser but a steam main which just happens to be vertical? And if it's the third floor, that's 20 feet of pipe which needs venting.

I would prefer to have it on the riser, as near the top as possible, but that's not easy. I'm intrigued by the idea of double venting the radiator -- one fast one right at the top, and a regular one a quarter to a third of the way up. The one at the top would act as a riser vent to a good extent, and the lower one would control the radiator in the usual way.

foresthillsjd

@Jamie Hall so, I had an idea and I want to know how crazy it is. What if I just add a nipple to the top of the riser, connect the elbow and shutoff valve to that, and just put my radiator on a little platform? (pitching it backwards) Then, could I just put a vent into the nipple? Then I've basically extended my riser above the floor to give me access for a vent. Also, if I screw up tapping a hole there, I haven't ruined the entire pipe...


@JUGHNE, before the vaporstat, I was running 1.5/1.0 and the problem was still that the thermostat would shut it off before it the third floor got hot. I installed the vaporstat to help throttle the morning recovery from the overnight setback.

Thanks for all your ideas so far. This is a very interesting discussion.

Jamie Hall

Sounds like a plan.

Setbacks -- even with a system which is functioning almost perfectly -- can be problematic; in systems which are even slightly uneven in heat distribution or boiler which are sufficiently oversize as to cycle on pressure they can make that uneven distribution much worse.

cross_skier

Here's my riser venting solution, it has worked well for two decades -- 1/8" Gorton on 1/8" street elbow.  My ceilings are very tall.  The risers vent fast with the biggest size orifice.

Jamie Hall

Yep. Looks good!

Mike Cascio

Two questions that need to be answered.  

1.   Is the vent on those third floor radiators closing ans getting hot?  I know everyone is saying that is the issue but is the steam even making it up there?

2.   Were the third floor radiators added at a later date.  How does the piping come come the 2nd floor to the third floor?

I suspect there may be a piping issue rather than a venting issue.  

EBEBRATT-Ed

Venting the risers is discussed in the LAOSH as removing the 90 deg radiator valve and installing a tee with a riser vent on it and reconnecting the radiator with a straight radiator valve. Frank Gerrity's method

cross_skier

That method got ruled out by my SO who had strong feelings about the iron tees being ugly

mattmia2

foresthillsjd said:

@Jamie Hall so, I had an idea and I want to know how crazy it is. What if I just add a nipple to the top of the riser, connect the elbow and shutoff valve to that, and just put my radiator on a little platform? (pitching it backwards) Then, could I just put a vent into the nipple? Then I've basically extended my riser above the floor to give me access for a vent. Also, if I screw up tapping a hole there, I haven't ruined the entire pipe...

Just use a tee as @EBEBRATT-Ed suggests or on some other configuration instead of trying to tap a nipple.

Since you have that huge bushing in the end of the radiator you could adapt that to a main vent, possible with a street ell or nipple and ell.

EBEBRATT-Ed

@cross_skier

What's the old saying? "It's better to beg for forgiveness than ask for permission"

EBEBRATT-Ed

You have the tapping 6" up the bushing on top and another tapping on top. Put half a dozen vents on that and see if it works then figure out how to do it so it will look better,

Avent on the riser in the basement will help some in addition to 2 vents on the rads it might be enough

foresthillsjd

Mike Cascio said:

Two questions that need to be answered.  

1.   Is the vent on those third floor radiators closing ans getting hot?
 I know everyone is saying that is the issue but is the steam even making it up there?

On a regular cycle, the one that happens about every hour when triggered by the thermostat, the steam never even makes it up there before the system shuts on pressure. If I try to force the issue by raising the thermostat a few degrees, by the second second cycle, the steam will fill half the radiator, but it's not blazing hot like the ones on the lower floors.

Mike Cascio said:

2.   Were the third floor radiators added at a later date.  How does the piping come come the 2nd floor to the third floor?

I suspect there may be a piping issue rather than a venting issue.  

The third floor radiators are original to the house. Their supply pipe is a straight shot from the basement.

foresthillsjd

EBEBRATT-Ed said:

You have the tapping 6" up the bushing on top and another tapping on top. Put half a dozen vents on that and see if it works then figure out how to do it so it will look better,

Avent on the riser in the basement will help some in addition to 2 vents on the rads it might be enough

Ed, I've read all of Dan's books, albeit a long time ago, but I'll be the first to admit that I don't have any practical knowledge. What is "tapping 6" up the bushing on top"? Do you mean make a little antler of radiator vents off the hole for the current vents? Which hole? The upper or the lower one?

foresthillsjd

EBEBRATT-Ed said:

Venting the risers is discussed in the LAOSH as removing the 90 deg radiator valve and installing a tee with a riser vent on it and reconnecting the radiator with a straight radiator valve. Frank Gerrity's method

I must have missed that part when I was reading. In NYC, I'm so used to seeing those vents like what @cross_skier posted that that's what I always assumed venting the risers was...

JUGHNE

It seems the simplest thing to do first would be to get the Allen head plug out, (the 6" up tapping) and then add another vent there. Keeping the high one also. IMO

EBEBRATT-Ed

@foresthillsjd

I would put extra vents on the rad for now. I would put a big vent on the lower vent.Not as a permanent fix but just to see if you can get it to heat on a normal call from the thermostat.

If that works then we can figure out how to vent the riser

Jamie Hall

A side note... if the boiler shuts off on pressure relatively quickly, either it is way oversize (quite possible) or the mains venting is very inadequate (also quite possible). Or both.

foresthillsjd

@EBEBRATT-Ed I have had these two vents on there since yesterday.  Top one is a Maid o Mist D and the bottom one is a Heat Timer varivalve on the max setting.  Currently, it’s 66 degrees up there and 72 on the first and second floors.  I don’t think the steam is getting up there at all in 8 oz of pressure.  Do I just crank it back up to 1.5 pounds?

I do want to get the main venting sorted out, but that’s a whole can of worms.  I currently have these vents on that main, but when I tried to put in faster vents, they were all too tall.  And most of the piping is behind a soffit, which I would open if necessary.  But it’s a tangled mess back there. And one of the vents is hissing, but I have ordered a replacement.  

I was going to try to add more to the end of that antler, but since the pipe is pitched, every addition has less head space.  

foresthillsjd

foresthillsjd

JUGHNE

Has anyone had success with adding rad vent on the inlet valve end to vent the riser?
I tried this once for a long horizontal run out and it never seemed to vent until the regular vent closed on the other end.

Jamie Hall

On pressure. If the steam isn't getting there on 8 ounces, 1.5 pounds isn't going to help. One of the fundamental maxims: if the air can't get out, the steam can't get in. But there are two others: if there's water in the way, the steam can't make it. And if there is no insulation, the steam will be very slow.