Venting short mains

ez011

I have a one pipe steam system with a 3 year old gas boiler. It takes 15-20 minutes for steam to first get to the radiators and I've been trying to shorten that time. The pressure is set low.



I have two short mains with long runoffs that go to all of the radiators. There are no vents on the mains and from I can tell, there never were. I assume this is because they are so short when compared to the runoffs and risers. I've had a couple people take a look and they didn't think installing a main vent would do much because they are so short (the supply lines are approximately 8ft and 7ft).



Everything I've read states to vent the mains but I haven't seen any examples with shorter mains and longer runoffs. Does anyone have any thoughts or recommendations for this setup?



Attached are photos of the two mains and boiler (I plan on insulating the main that isn't insulated).



Thanks

Jamie Hall

This is a situation

where I would seriously consider putting vents on the runoffs, before they got to the radiators -- particularly if you have runoffs which are either really long or which serve two or more radiators.  Otherwise you are depending on the radiator vents alone (obviously...).

nicholas bonham-carter

Please place insulation on the supplies!

Sorry, I just went through the self-checkout at the big box store, and the computerized nagging is still with me.

Those mains need insulation, even if only with fiberglass batts as a temporary expedient. I agree with Jaimie that the mains need venting, but if that is not easy, then putting fast vents on the end radiators, and slow ones on the rest may suffice. Get to know your pressure, and keep it as low as possible (ounces if possible).--nbc

Hap_Hazzard

Insulate the runouts too

You could be losing a lot of steam through the runouts. Being smaller, they have more surface area per volume than the mains. Insulate as much of them as you can reach.

ez011

Runoff vents

Thanks for the great feedback.  I will be insulating the mains and runoffs ASAP.



Are there any downsides to adding vents to the runouts as Jamie suggested?  I have eight runouts that are longer than each of the mains so I would most likely have all eight vented if I pursued this option.



NBC, my cut-out is currently set at 2 and differential is at 1.5 (I have a subtractive pressuretrol).  Is there anything else I should be doing to manage the pressure?



Thanks

nicholas bonham-carter

pressure management

i hope you have a good low-pressure gauge, on the same pigtail as the pressuretrol, as the pressuretrol is quite inaccurate.--nbc

EEngineer

I don't think so

Think about it: Just filling the mains quickly is not enough, you want to fill all the supply lines to the radiators as quickly as possible, too. In your case the runouts are actually part of the mains.You want all of those filled and heated as quickly as possible to make sure that steam starts getting to all radiators at about the same time and as quickly as possible.



I would then use variable vents at each of the radiators and adjust them so that all radiators filled and heated at about the same rate: more venting on large radiators, less venting on small radiators. The goal is to make suere that all radiators are filled and hot at the same time. Odds are that one or two radiators control the area where the thremostat is. You want make sure that all radiators are hot by the time they satisfy the thermostat or you won't get heat from the radiators at the end of the chain. You may even have to choke down large radiators in the thermostat space to make sure the thermostat is not satisfied before radiators at the end of the system are filled.



Sorry, I put this in the wrong place... no way to delete a post?

EEngineer

Vent the runouts

Think about it: Just filling the mains quickly is not enough; you want

to fill all the supply lines to the radiators as quickly as possible,

too. In your case the runouts are actually part of the mains.You want

all of those filled and heated as quickly as possible to make sure that

steam starts getting to all radiators at about the same time.



I

would then use variable vents at each of the radiators and adjust them

so that all radiators filled and heated at about the same rate: more

venting on large radiators, less venting on small radiators. The goal is

to make suere that all radiators are filled and hot at the same time.

Odds are that one or two radiators control the area where the thremostat

is. You want make sure that all radiators are hot by the time they

satisfy the thermostat or you won't get heat from the radiators at the

end of the chain. You may even have to choke down large radiators in the

thermostat space to make sure the thermostat is not satisfied before

radiators at the end of the system are filled.

crash2009

Missing Vents

Somebody with a lot more smarts than me piped it that way for a reason.  Why they did not use a more traditional approach to main venting is beyond me.  In the past the main vents were likely up here in green.  The second return was likely below the waterline.  Actually much lower than I have it drawn in the picture.



Do you ever have to add or remove water from the boiler?

crash2009

A main is a main

The more I think about it,  those returns are just plain WRONG.  You need main vents on both of them.  Each return must drop to the floor (below the waterline) where they are tied together.  The Hartford should start at the floor, then come up to the boiler.  The fresh water feed should be lower too. 



Short main or long main, a main is a main.  It needs to have a vent, and a proper return.  I will ballpark the amount of air you have in your mains at .600 cubic feet.  You should have at least a Gorton 1 on each return.



The clean install had me fooled, The installer did not read the manual.

ez011

More problems that originally thought...

I haven't had to add/remove water to the boiler other than when it gets really dirty.  Both returns connect up above the boiler.  The second return is coming through the wall that is difficult to see in the photo.  I guess I shouldn't be surprised it is piped wrong since the installer also set the pressure really high.  I turned it down when I started doing my own steam research after installation (these resources are invaluable for someone like me).



So here's my plan of attack:



1. Insulate the supply lines.

2. Have someone that knows what he's doing re-pipe the returns so they

come together below the waterline and add two main vents to each

return.  I currently have water hammer at the end of the cycle so this

may solve that problem too.

3. Add main vents to the eight long runouts and adjust the radiators accordingly based on size.

4. Look at replacing the pressure gauge since I'm fairly certain mine isn't a good low-pressure gauge.



In total, I'm looking at 10 main vents.  Two on the returns and eight on the long runouts.  Let me know if there is anything else I should be aware of or if I misunderstood something.



Now to find someone that knows what they're doing in the Boston area.

crash2009

Water Hammer

at shutdown points to the Hartford Loop/Equalizer connection,  fixing the returns might correct the problem.



1-Insulation definately.

2-at least one vent on each

3-possibly do something, have the pro come up with something

4-yes 



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