Balancing heat

webbrewers

The system:

1 pipe steam with a main pipe running the perimeter of the central part of the house (8 rads) and a secondary main that feeds a smaller "wing" (5 rads). The secondary main is located in the first quarter of the main pipe and both loops have their own main valves.

The problem:

Since replacing the boiler, the rads at the far end of the main pipe aren't getting heat as they used to. The boiler has to be running a long time (30-45 mins) before they start to get steam. The secondary main heats up very fast - I'd like to even out the steam distribution a bit and help the rads at the end of the system.

I've checked the main valves, the pitch of all the rads and the rad vent valves.

There's a mix of vent valves with mostly Varivents set to minimum on the rads that get steam fast, and non variable vents on the rads at the end of the system.

I've read mixed reviews of Varivents with some saying they vent too fast even when at the "closed" setting. So I'm wondering what the best arrangement is.

Also, the new boiler has a lower btu rating than the old one, but the hvac guy was confident it was sized right for the system. And we're now power venting the exhaust through a side window rather than using the decrepit chimney.

nicholas bonham-carter

New smaller boiler

If the installer measured the radiators, and found their edr, radiation capacity, and then sized the new boiler to that total, then the size will be right.

What pressure is the system attaining? Have you got maximum main venting?

Try some Hoffman 40's on the radiators, and see if the steam arrives at all the radiators simultaneously.--NBC

ChrisJ

Venting

I kind of agree with NBC except for me, a Hoffman 40 is way too slow.

My boiler is very closely matched to my load, yet I currently have Gorton 5s, 6s and two Cs on my radiators.  I still have a few Hoffman 1As as well as I don't have money to replace them with Gorton's yet, but those are set to vent fairly slow, probably around a Gorton 4.



Because of my system having several long runouts (10 to 20 feet long) I need a LOT of venting on those radiators.  However a Vari-vent has no place on my system.  I had four of them which were brand new and I gave them to a friend to use as main vents.



I highly recommend you buy a copy of this, I wouldn't have been able to balance my system without it.

http://www.heatinghelp.com/products/Steam-Heating-Books/25/146/Balancing-Steam-Systems-Using-a-Vent-Capacity-Chart-by-Gerry-Gill-and-Steve-Pajek



 I also recommend ditching vari-vents and buying the appropriate sized Gorton's. With a properly matched boiler, varivents will NEVER allow you to heat evenly, its just not going to happen.

Maine Vent

Same problem with mine

Just a homeowner, but I have followed the advice from many of the Pros' and Semipro homeowners on this site. Here is my 2 cents.



1. Make sure, I mean really make sure that your burner input is matching your radiator EDR

Mine was way underfired last winter, boiler ran and ran rads didn't heat well

This year after 2 increases in my gas orifice for my burner, I have really quick steam to end of my main vent. All my rads get hot and stay hot. So you need the right amount of fired to make the right amount of steam.



2. I, too have used Varivalves on my rads, I took them right off they would not balance the heat at all. I tried many different theories to get these things to work. The Deadman say " Vent the rads slow". Thats proven advice.

I put Hoffman 1A's on all my rads, set the all at #1 setting I could not believe the results.

Next heat cycle after the Hoffmans were on, even heat and plenty of it.

3. Max out your main vent with some groton #2s, your pressure will drop to ounces or less, and you will get quick steam.



I found a very reliable young heating tech, who loves steam, and is great with natural gas.



Listen to what Dan says in his books, and also to the Deadmen, They worked out all the bugs, it is some kuncleheads that are putting the bugs back in.



My 2 cents, good luck

jumper

steam is old

If the windows have been improved the rads have excess capacity. I agree with MaineVent and everybody else that slow rad vents are the way to go. If any room is too warm you can enclose that radiator to cut down its output. Or cover it partially. In an extensive rehab enclosures can have shutters or dampers to adjust heat output.



So balancing is doable even after the building is better insulated. But then there may be a short cycle issue in mild weather. That's why vacuum systems were tried.

webbrewers

I appreciate all the responses..........

I appreciate all the responses (which I missed because notifications went to junk folder).

The pressure is set low at .5. Both loops have main vents - I'm not sure if they are "maximum" venting or not. Is there a way/recommended valve to slow down the secondary main? That might help push steam through the main loop.

I'll check with the boiler guy on the gas orifice - he came back to try and help with the balancing but I don't think that came up.

The infrastucture should be okay because the old boiler did reach the furthest rads even when it was on its last legs. If anything it's a little better now because I repitched some rads and cleaned up some valves.

The valve consensus seems to be avoid Varivents.  I'll check out the other links and see if a few new valves help.

Another issue is it's a large 1876 house with 10-11' ceilings, original 90" (leaky) windows and the thermostat is in a room that gets heat fairly quickly. I may also try turning off one of the rads in that room and see if that evens things out a bit.

Thanks again for the tips.  

 

Steamhead

Measure

the length and diameter of each steam main, and tell us what vent is on it. We can tell you whether you need to upgrade. Proper main venting will go a long way toward balancing your system.

webbrewers

Here are the measurements:

Here are the measurements:

Main            Pipe         Length    Risers

Main 1         3.5"          32'            1 x  14'

Main 1         2.5"          47'            4 x  14'

Main 2         2.5"          70'            2 x  14'



Main vents:

Bit hard to see but looks like both mains have Gorton #1A. 



Thanks for any help.

BobC

Gorton #2's

Assuming you have 3 mains and main vents and the 3.5" OD pipe is actually a 3" pipe and the 2.5"OD is a 2" pipe I would replace the Gorton #1 main vents with Gorton #2's.  Then add #1's  alongside the outside two mains that contain about 1.5 cu ft of air each, the middle one looks like about a cu ft of air so the #2 would probably be ok for a start. The Gorton #1 is rated for 0.33cfm while the #2 is 1.1cfm.



With the mains adequately vented I would get rid of all the VariValves and use very slow vents on all first floor radiators and slightly faster vents on upper floor or slow to heat rooms. This may take some experimentation to find the right mix of vents so finding a knowledgeable steam pro would help.



Bob

ChrisJ

Multiples!

I would have to recommend multiple Gorton 2's per main. I don't think one each is enough.

webbrewers

To clarify.........

There are only 2 mains. I separated them into 3 because the primary main has 32' of 3" pipe and then reduces to 2".  See attached pic.

Then add #1's  alongside the outside two mains that contain about 1.5

cu ft of air each,



Do you mean add an additional vent to the main?

And is the cu ft of air the estimate of what needs to be pushed out?

Jabbott1

pipe volume.

Main 1 has a volume of 1.64+1.1 which = 2.74cfm



Main 2 is 1.63cfm



A gorton 2 flows 1.1cfm and gorton1 flows .330.

So you can use any combo of valves to get to the amount of vent you need.

so for example on main 1. 2 gorton 2's and 2 gorton 1's = 2.86

webbrewers

Ah hah

...I think I'm finally getting it (my brain doesn't "vent" too quickly these days).

It makes sense that the shorter, secondary main is "stealing" the steam before the primary main gets filled.

If I wanted to add additional vents to the primary main, is it a matter of adding a T fitting and attaching them to that? I don't fancy cutting into 90 year old pipe. 

BobC

Build an antler

You can come off the main with an elbow and then use nipples and T's to add as many vents as you need. make sure this antler has slope to it so water can find it's way back to the main. Also the Gorton #2's have 1/2" threads while the #1's have 3/4"



Can you show the location of the vents and the interconnection between the mains on your diagram, I'm having a hard time visualizing the interconnections.



Bob

webbrewers

Image

The problem area is at the end on the primary main.

SWEI

image problem

opening in a new window made it readable

webbrewers

No, the.....

gray dotted lines are the returns. The secondary main is fed about half way down the first run of the primary main - loops around and then after the vent returns to the boiler. That vent is actually much further from the boiler than the pic shows. I can't get the newer pic I added to show in the pop up - maybe that's the problem? 

BobC

Try this

The way the second main comes off the first main can be a problem, how the steam divides at the split between main one and two is chancy. It would have been better if they fed the second main off a second feed from the boiler header but changing that is not easy and definitely expensive.



With a clearer understanding of your piping I would use 2ea Gorton #2's on main one and 1ea Gorton #2 and a Gorton #1 on main two.  You might not need the two vents on main two but be prepared to add it if you have to. Leave room so additional vents can be added if needed. Understand that the venting balance might have to be adjusted once you have put the proper vents on the radiators.



The goal is to fill the mains with steam fast so it will be available to all radiators at about the same time. Varivents on your system are likely to cause more problems than they solve, I would use slow vents on radiators that seem to heat quickly and faster vents on ones that don't.



Bob

Hap_Hazzard

Returns

Are both returns below the minimum water line before they meet?

webbrewers

Responses

@hap-hazzard:

Yes, both return lines feed back below the min water level at the back and I had them put in a Hartford loop which wasn't present before.

@Bob C:

With all the advice here and some reading, I'm beginning to realize how messed up this system is........ I just timed it from cold and it took about 20 minutes before the primary main vent closed. Meanwhile the secondary main was still venting so it doesn't seem as though it's stealing all the steam as I thought. I also noticed the last rad on the system huffs and puffs exhaling air but then starts sucking air back in until it resumes exhaling again which seems odd.

Getting the mains properly vented is job 1, then I can tackle the rads.

Thanks for all the advice!

    

ChrisJ

Cold start

That depends,

My system from an ice cold start where the boiler is room temperature it takes 15 minutes to produce steam. On a day like today where its in the 20s or 30s outside it usually takes 5 minutes or so because its been on recently.



Once it produces steam I get steam to the end of my 29' main in less than 3 minutes. In fact in 3 minutes after its steaming I probably have steam to my radiators on the 2nd floor though it takes a long time for all of the radiators to heat all the way across, probably a good hour for every radiator to end up completely heated.



I installed multiple Gorton vents and fast vents on all radiators last year. I ended up with cold radiators so I backed everything off and slowed up my radiator vents big time. Then over time I increased them more and more. Now I have Gorton Cs on some radiators on the 2nd floor. It took a long time and a lot of patience to vent my radiators as fast as possible without causing balancing problems. I also had to insulate my steam mains as the boiler couldn't keep up.



Whats nice though is everything heats evenly and on mild days with short run times rooms on the 2nd floor still get heat.

webbrewers

Update.

@ChrisJ - yes I meant it took 20 minutes from a really cold start so now I don't feel so bad.

I did notice though that before the primary main was fully steamed, the low water cut off shut the burner off and I could hear condensate pouring back down a return. This happened a few times before there was sufficient steam. Is that normal? I suspect the mains being uninsulated is part of that problem - how much would that help?

I did have the boiler guy add a bigger mains vent - a Hoffman 75 (he didn't have Gortons which was what I asked for). I figured that at least if that improved things I'd know where the main problem is.

Unfortunately it's made little difference.



One bad rad has what looks like a non steam valve too. Looks like the pic  - can anyone confirm if this can be used for one pipe steam?