Fine tuning main venting

malex

Now that it's a bit nippy (13F) I decided to see how well my mains are matched in venting speed. Overall, the system is working very well since I put on a Gorton 2 on the 58' main and a #1 on the 15' and insulated the mains and run outs and put Gortons on all rads. The second floor master bedroom, which is 2nd to last on the long main is still not getting very hot but before I switch out the G#6 for a C, I wanted to optimize the main venting.



Since I have insulated the mains it is hard to tell when steam starts to move into the mains but from when the steam heats up the end of the short main it takes about 4 minutes before the end of the long main gets hot. Both mains are 2" and insulated. The 3psi guage does not move in this time.



Would adding a G#1 to the existing #2 on the long main suffice or do I need another #2. If a #1 has about one third of the venting capacity of a #2 then simple maths tells me that a #1 should be just about right but it feels like the steam had more than 15" to travel in the long main once the short main got filled. Does this make sense?

gerry gill

i would probably add a #2 vent.

remember that the cubic feet of air to vent is just one consideration..the steam is also condensing as your trying to move it which can't be accounted for in the math.

malex

More to it than volume

Thanks gerry, I figured it was more to it than simple volume math. In addition to more condensation in the long main I am assuming that it will create more resistance to push the 58' of air out than 15' and also, more steam will start to migrate into the 8 runouts on the long main compared to the 2 run outs on the short one, again adding to the need of more than volume proportional venting on the long main.

The 2 rads on the short main are the 2 closest to the thermostat and are vented with G#4s so if it turns out that the rads on the long main heats up to fast after adding a #2 then I should be able to vent them just a bit more and achieve balance.

malex

Added a #2

Received the additional #2 today and put it on an antler with the existing #2 and got the time from that the #1 on the short main heats up to the 2's on the long main get hot down to about 2 minutes (down from 4 with the one #2).



Should I add more venting to the long main and is it wort it? I'm somewhat of a perfectionist but don't want to give the fine folks at Gorton more of my hard earned bucks if it is just to satisfy the OCD I have developed around my steam system (can anyone relate?).



I guess I could replace the #1 on the short main with something slower but I don't want to. I like it.



I could increase the rad venting on the slowest to heat rads on the long main but I'm already experiencing some issues with all the condensate they create on a cold morning so I'm hesitant. I'm no longer using a set back and insulated the mains, which cured most of this issue but it still does not seem like the right thing to do.



This is really not a problem but rather trying to fine tune this adequately functioning system, and satisfy my inner 'dead man' so if someone just posted about a tripped relief valve, by all means respond to that first.

crash2009

oz gauge?

I think the speed (minutes) is going to change from day to day.  A more accurate way to measure might be by backpressure.  NBC has been telling us that for years.  I am just beginning to understand what he is talking about.  How hard does your boiler have to work (in ounces) to push the cold air out of the main.  You will know if you have enough vents when your gauge reads 1 oz while expelling the cold air from the main.  NBC, did I say that right? 

Do you have a 0-3 psi or an oz gauge on the boiler yet?

malex

backpressure

Yes, I do have a low pressure gauge and it only registers a flicker around 0 as the vents are heating up. So I guess I have enough venting and restricting the short main would be the best thing to do if I wanted to perfectly balance the main venting. But do I need to? Is a 2 minute difference within the range where you should start tinkering with the rad venting instead for balance?

crash2009

Wait until its gets cold again

just watch it for a few days before you make up your mind. 

nicholas bonham-carter

the importance of back-pressure

well put crash! that simplifies it: putting it in terms of how hard the boiler has to work [how hard do the fuel suppliers have to work, at our expense]!

one more point to consider when calculating the volume of pipes etc, would be in making allowance for the capacity of the steam chest of the boiler itself. all that air also needs to be allowed to escape. this where the ounce gauge become invaluable.

malex, when you see the needle flicker on the gauge, is that a 1 ounce flicker, or a 2 ounce flicker? ideally i would like to place hoffman 40's on all the radiators to begin with, and the fine tune by increasing any radiator vents where there would be long risers/run-outs etc. this would ensure that in the initial venting phase, the mains fill completely, before any steam has started to move up any of the risers

when you have the sort of generous main venting, i recommend, then the air velocity through the vents is lower, and less likely to carry dirt from the mains into the vent body plugging them up.--nbc

malex

.1 psi

The gauge show just over the 0 mark up to .1 psi, which if I understand correctly is about 1.59oz but to me it would be hard to read much less pressure. (this is har math for me as I grew up on the metric system where everything is divided in 10s)

crash2009

Canadian Aye?

I grew up with the metric system too.  Everybody around here always talks in ounces.  I got tired of doing the math.  I ordered a 0-20oz gauge.  Another thing that helped was the Ray Porous Metal Snubber (Model 722BG) 1-888-SNUBBER.  A snubber is installed in-between the gauge and whatever the gauge is screwed into now.  What it does is take away the fluctuations of the gauge needle.  It makes the gauge easier to read.  1.59oz sounds pretty good.  You getting any water hammer yet?  If not keep adding until you do, then take one off.  That up and over main of yours kinda scares me though.  Well I guess it will let you know when you have too many Gorton 2's.

malex

Close enough

Swedish actually, but same cold climate so heating is in the genes. Snubber sounds like a good idea.



Why would I get water hammer as I added venting? Does the steam travel too fast? I did develop some hammer in one rad after I insulated but I think it is because I raised up the main over the beams and pushed it down in the ends. I must have changed the pitch in the riser so I will have to break the plaster ceiling to check it out (and its more of a slow tapping which speeds up until it get quieter and quiter and ends).



Other than that the 45sover the beams are not causing a problem. I had raised up the main on oak blocks but got terrible expansion noises so I hung the main using clevis hangers and 1x1 hardwood dowels stuck into cut outs in the fiber glass. See pictures (not as nice as yours but an improvement)

crash2009

Water hammer

 If you vent too fast, water hammer is one of the risks.  Fast venting means fast steam.  If steam picks up some water on the way to the end, you might get some hammer.  If you don't hear any no problem.  Small hammer sounds like ting, ting, ting.  you can hear it bouncing off the elbows.

Personally my plan was to add vents until I got hammer, then back off.  I have not reached that point as of yet.  Don't know what yours will do, you will have to experiment.     



Thanks for the complement.  You did a fine job on insulating yours.  Both of us did a pretty good job for the first effort. 



And for those of you that are just thinking about it, it doesn't matter what it looks like, just get it up there.