uneven heating

tony_19

Hello everyone I guess this is the same old story ...the situation is this a 3 story building with 3 apts in the front and 3 in the rear. the apts. in the rear heat up much faster and hotter than the the front apts. the boiler is located in the rear of the building the main to the front is about 80 ft. with 2 maid o mist main vents. the rear main has no main vents it is located about 10 ft from boiler . the radiators are all the same size in the apts. i have installed various  sizes gorton vents on the radiatiors the smaller sizes near the boiler and larger as we go up. i have even installed double vents on the radiators in the cold apt. and also did the modification from the book lost art of steam heating by installing a main vent there and straight shutoff valve.  for that apt. get really hot the thermostat has to be raised where the apts are overheating.  any suggestions would be appreciated. thank you



tony

nicholas bonham-carter

same old story

well it's the same old problem, and the same old solution.

have you looked for any main vents in your system? until you get them working, you will be paying lots of money to your fuel company to force the air out of your system. in addition, the occupants of the building will have plenty of complaints about uneven heat!

get those main vents back in operation. you may need to change the radiator vents  to slower types when you have got the mains functional.--nbc

tony_19

same old story

thank you for your response.



do you think i should change the main vents the longest run has 2 maid o mist #1 the shorter one which is about 10 ft from the boiler has no main vents. also should i vent a branch of the main before it goes into a riser. another  thought i had to change all the radiator vents to the same size like the hoffman 40.also should i add more main vents on the longer run which is about 80 ft.



thank you



tony

nicholas bonham-carter

main vent selection

for a start, i would put the maid o mists on the shortest run and a couple of gorton # 2's on the longest run. a good low pressure gauge [gaugestore.com-0-15 ounce] would show you the back-pressure during venting which should be 2 ounces at most. after you have made the venting changes, you may still need more on the shorter run, because i don't think the maid o mists are very capacious. remember, you can never have too much main venting. ironically, steam travels quickest at low pressures in the post venting stage, so the gauge would show you the steaming pressure as well.

when you are sure that the horizontal mains are venting as quickly as possible, then you could change the radiator vents to something slower like the hoffmans, reserving any larger ones for top floor radiators.--nbc

Dave in QCA

Is the load balanced between the 2 mains?

You have indicated the difference is between the front and back of the building, and that there was a 10' long main in the back and an 80' long main for the front.  I am going to assume that 1/2 of the radiators are on one main and 1/2 are on the other.  Even if not, it may not make a huge amount of difference, in that the radiators and risers closest to the boiler are getting the steam first.



The vents you have on your front main are woefully inadequate.  I just ran that calculation assuming that you have 4" main running to the front.  You really need to have 2 Gorton #2 vents there.  That would vent that main in between 2 and 3 minutes.  The recommended approach to venting mains is that all mains should be properly vented at a rate that allows steam to reach then end of the main in about 3 minutes.  I hesitate to say this, but in the scheme of your building, and the fact that the back getting way to much steam, I think that you may be just fine without putting a main vent on that 10' long main.  If you find out later that steam is not reaching the end of the 10' main at the same time as the 80' main, you can add a vent, and one of your existing Maid 0 Mist #1 vents at .33 cfm @ 1 oz should be fine.



The second part of getting good steam distribution (Remember, vent your mains fast and your radiators slow and completely.)  is to make sure your radiators are venting slow.  The common method of balance recommends different sized vents for different sized radiators, but your radiators are all the same size.  It normally is not necessary, to put in different sized vents to try to balance the system, at least not initially.



I would recommend that you install Hoffman #40 vents on every radiator in the building.  They are slow, but not too slow, reliable, and quiet.  Slow rad venting, FAST main venting, and riser vents, that you have already installed will hopefully straighten this out.



Normally, it is not necessary to vent lateral branches to the main.

tony_19

uneven heating

thank you for all the info.....



i believe the main is either 2.5" or 3" . also i measured the radiators today and they are 36" high by 9" wide and there is a 3 section and 6 section and 8 section should i vent this with different valves or just use the Hoffman 40 for all. on all 3 floors. and also the risers that are used in the kitchen and bathroom have Gorton D with 1/8 " is that sufficient? 

tony_19

low pressure gauge

thank you for all your help



is the gauge you  are talking about on gauge store.com

the





















Low Pressure Gauge 2.5", 0-15" H2O







Stock #:

33004



Brand:

WIKA



Series:

611.10



Mfr Part #:

9851682

tony_19

low pressure gauge

would i install the gauge of a tee in line with the vents so it shows the pressure at the vents.

Dave in QCA

Not all the same size?

The Hoffman 40s might work fine, but given that they are not all the same size as I thought you had indicated they were, some of the others on here might have some advice as to what vents you would use.

nicholas bonham-carter

low pressure gauge

 it is wika, but make sure it is 0-15 ounce, not inches of water.--nbc

Steve_175

Vents

If you have a 3" main you will need 3 Gorton #2 vents to sufficiently vent the 80' run.

The set up should look something like this.

http://www.gwgillplumbingandheating.com/webapp/GetPage?pid=415



You can get them here.

http://www.pexsupply.com/Gorton-G2-Gorton-No-2-Straight-Air-Eliminator-3524000-p

Dave in QCA

That would vent REALLY fast!

Steve, 3 Gorton #2 vents would vent that 80' x 3" main in 1.28 minutes @ 1oz pressure.  That is assuming that the main could be heated that fast and that the connection for the vents is 3/4" pipe or larger.



Agree that you cannot overvent a steam main.  Just wondering is you are really aiming for a venting rate that would be that fast.

BobC

Venting

Radiators are usually vented according to the size (in sq ft), if your radiators vary from 3-10 sections you will probably need more venting on the large ones because there is almost a 3:1 difference in size. Upper floors may need more venting also because the piping starts to get a little more significant. Always remember best operation is usually achieved when you vent the mains fast and the the radiators slowly but completely.



Once you get the basement mains venting straightened out (at least 2 Gorton #2's on the long main and maybe a Gorton#1 on the short one) you might want to try some adjustable vents (Hoffman 1A's or Ventrite #1's) so you can dial in the venting. just leave the Hoffman 40's on the small radiators and use the asjustable vents on thae large radiators that don't heat up fast enough. That way you should be able to get them all to heat up at about the same time.



Bob

Steve_175

Vent Rates

From what I have learned here you want to vent your mains as though there was an open pipe at the end of the mains. And if your boiler is sized right it should be pushing steam down the end of the mains within a few minutes of steam being produced in the boiler.

tony_19

venting

well i installed the 2 gorton no. 2 and i will see tomorrow if it is working better.

Steve_175

What happened

How is your system doing now?

tony_19

needs fine tuning

as i said i installed the gortons now i need to go to each apt and install the vents i am thinking of installing the hoffman 40 in the backside of the building which is right above the boiler and the hoffmans 1a in the top fwd apt where the thermostat sensor is installed now...8