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Joined on October 21, 2011

Last Post on April 1, 2012

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vent your radiators slow

@ January 12, 2012 8:31 AM in Location for #2 radiator vent

"Vent mains and risers fast, vent radiators slow"

That is all.


@ January 11, 2012 10:05 PM in How many CFM of steam does a certain boiler make?

thanks bob!

doubt it will work at 1 oz.

@ January 11, 2012 9:14 PM in Location for #2 radiator vent

what type of a steam system is this? If it's 1-pipe, I seriously doubt it will work well at 1 oz. 

How many CFM of steam does a certain boiler make?

@ January 11, 2012 9:00 PM in How many CFM of steam does a certain boiler make?

All in the title.

Is there a way to calculate how many CFM of steam does a certain boiler make? Ignoring the effects of condensation.

Rethinking 1-pipe steam venting strategy

@ January 11, 2012 8:18 PM in Rethinking 1-pipe steam venting strategy

I'm doing a complete revent tomorrow of a third building. 19 unit building, 4 rads per unit.  I'll be changing out 76 vents.  On the first 2 buildings I did last month, an typical  venting strategy has caused me some balancing problems.  I'm using MOM vents on the rads and Gorton 2s and 1s as needed on the mains. Yes, I quickly vent all the mains, the longest mains with multiple G2s.  Mains fill with steam within 4 minutes. Just about as fast with an open pipe at the vent. But  for 1-pipe systems with this many radiators the typical venting idea that most rads get 5s, larger rads get 6s, far/cold rads get C and small rads or rads in rooms with the thermostat get 4s, and maybe far/cold/rads on the third floor might need to be stepped up one step to vent the riser, the amount of radiator venting exceeds the venting available at the mains.

Just as an example, I added up the main venting on one building. total venting on the mains is 5 G2 and 2 G1. This is 6.16 CFM at 1 oz.
The 76 vents on the radiators vent at 7.216 CFM at 1 oz. And if you calculate the radiator venting at 3oz  it comes out to 21.702 CFM.  I believe that this is too much venting on the radiators. I have decided to try a more conservative (aka slower) venting strategy on the radiators on this third building. All radiators will be getting MOM #4 with the following exceptions. Add 1 size for 3rd floor rads.  Add 1 size for "very large rads".  That's it. On this building I'm doing tomorrow, that give me total radiator venting of 2.08 CFM at 1oz and 10.6CFM at 3oz.
With the additional "backpressure" I should be able to get steam to go where I want it to, not where it wants to.
Any comments?

adding a second vent

@ January 11, 2012 7:25 PM in Location for #2 radiator vent

Isn't there a spot for a vent on the valve side (opposite side from your picture) for a vent there?  the end sections for radiators are usually the same.  You can add another D to that valve side.  The benefit is that once the riser is vented and steam hits the first section, you close up that vent and vent the radiator just using the 1 D on the far side.

tenant is now cold?

@ January 11, 2012 7:20 PM in more venting, another rad, and / or bigger pipe?

she probably "feels" cold because it was so hot before ;-)

pressure not velocity

@ January 11, 2012 7:15 PM in Drop Header Sizing......

You increase the header to lower the exit velocity of the steam.  High velocity steam will pull water with it giving you wet steam (bad) vs. dry steam (good).

temp logger

@ January 11, 2012 9:09 AM in VisionPro 8000 settings

I've used an Exetech temp logger.  Works real well.  I checked out the Lascar and it only allows 30 min intervals. I wanted something closer to 5 minute intervals.  Exetech does down to 30s intervals with 30,000 data points


@ January 10, 2012 11:20 PM in Balancing Problem In Old Multi-Family

I kind of prefer the "non-adjustabillity" fixed vents for rentals.  I've already had some tenants unscrew the orfices out of the MOMs.  Once I get this one building balanced, the MOM orfices will be getting loctite.

I think Dole went of out business, no?

what kind of pipes in the house and how old?

@ January 10, 2012 10:36 PM in Pressure Booster on Hot Water

Iron or copper lines?

If iron, how old are the pipes?
I have 3/4" lines (copper) serving three baths on a stacked riser and the 3rd floor (35 feet up) has more than adequate water pressure for a shower. Incoming water pressure at the meter is between 45-50 psi.

MOM #4 vs. Hoffman 40

@ January 10, 2012 10:28 PM in Balancing Problem In Old Multi-Family


Is't a MOM #4 half the venting capacity of a Hoffman 40? What do you mean by a "traditional" vent?  I need something between a MOM#4 and a MOM#5 on my other problem building.  I'm thinking of drilling the removeable orfices on the MOM vents with a drill a bit bigger than the MOM #4 hole.

slow down the radiator venting

@ January 10, 2012 6:07 PM in Balancing Problem In Old Multi-Family

 Vent your radiators slower. Way slower.  Way way slower.  I've been battling a problem with a multi-unit building for about 4-5 weeks now. I was using Cs, a couple of Ds, and a lot of 6s and 5s. Close in radiators are literally stealing steam from the radiators that are furthest out.  I'd say use 4s for all small radiators and 5s for the larger rads.  Nothing bigger than a 5 for now.  Run it a few days like this and then you can determine if you need to bump up a vent a size.

Make 100% sure your mains are vented as fast as possible.

thermostat lock boxes

@ January 9, 2012 9:29 PM in Landlord question

nix the thermostat in the box.  I've had tenants use knives and screwdrivers thru the vent holes to fiddle with the thermostat.  nbc's idea of the remote sensor will be a better solution for the minimum, then wire in a parallel for the tenant to play with.

riser sizes

@ January 9, 2012 9:07 PM in Riser Size

See page 14 and 15.
Near boiler piping needs to match manufacturer specs.  You can go back to 2" at the output of the header.

increasing vaporstat cutout/cutin

@ January 9, 2012 9:03 PM in Location of main vent

Dave and Mike,

I saw these posts this morning about turning up the vaporstat at bit to get more pressure. Vaporstat is now at 13 cut out and 7 cut in.  I'll let it run for a few days like that and see what change that makes.

additional vent station added to Main #1

@ January 9, 2012 8:37 PM in Location of main vent

Pics of a 2nd vent station added to the main vented by V1.

I have 2 G2s and 1 G1 at this station. The original V1 station has 2 G2s and 1 Mepco 2E.  Up until this new station gets hit with steam, The main is being vented by 4 G2s, 1 G1, and 1 Mepco 2E. Pressure at boiler is now hardly hitting 1 oz until all main vents are closed up. This should be about 6.26 CFM. Wisps of steam arrive at the new vent station at about 4:15 after boiler starts steaming. I ran a cycle with my "manual" vent 1" ball valve seen in pics, wide open to test.  With ball valve closed vents heat up at 4:30ish.  So a 15 second difference with the pipe full open.  I am not really getting any appreciable amount of steam until about 20 minutes into the cycle. I think the steam is getting eaten up somewhere else.  It's almost like the main is not insulated, but it is.  

I am beginning to think that MOM #5 and #6 that I used on the radiators off main #2 and main #3 are helping to vent those mains too fast. I'm starting to think that I need to vent all the radiators off main #2 and main #3 with #4s.  I believe Dave mentioned Hoffman #40. The total venting of main #3 is 2.395 CFM. Total venting of main #2 is 2.395.  Total venting on main #1 is 9.36 CFM (3.08 radiators + 6.26CFM) 

By the way, this system used to run on a pressuretrol setting of 3.5PSI and 2/3 of the building used to use the double hung heat control method.

nice pics!

@ January 9, 2012 9:00 AM in Vintage beauty

That beast looks like about the size of a boiler I've got in a 19 unit apartment building.  How many sq. ft. of steam does that thing do?

checking pipe pitch

@ January 9, 2012 8:57 AM in Location of main vent


Thanks!  That give me an idea to do something similiar without all the rest of the "jig".  I can just clamp a 3" sinker nail to each end of my 8' and 4' levels.
Quick ASCII art:
If that makes sense, so that the nail will poke thru the insulation to the pipe.
Regarding your drawing, my main layout on this building is not exactly like you have it there.  Where you have V2 is actually a tee. The V3 branch starts there with a  back to back 45, so there's no way that condensate from the V2 branch can run into the V3 branch.
I'll be moving the V3 vent closer to the bath/DR runouts today.  I'll have some pics to post later tonight I hope. 

i'll check the level

@ January 8, 2012 10:51 PM in Location of main vent

Ok.  I'll check the level. Will be a pita, because all the mains are insulated.  Can I just check the level of the main from outside the insulation? 

The dry return from the main drops straight into the wet return. Goes no where else.

more reponses

@ January 8, 2012 10:27 PM in Location of main vent

crash, regarding the early closing on the G2s, I'm not worried about from the previous cycle.  I think the G2s are closing up when the current cycle starts and the condensate heats up the antler.  Because there's so much condensate (1200ish EDR) flowing into a 1-1/4" wet return, that pipe heats up within 3-4 minutes of the condensate flowing thru it and that heat transfers to the antler.

Mike,  HB Smith 28A-S-5 is rated at 3646 sqft. Connected EDR is 3250 sqft.  I've clocked the meter and burner is firing at 1.375MBtu at high fire 745K at lo fire.  Vaporstat kicks burner to lo fire at 12 oz and back up to hi fire at 4oz.  It cycles back and forth from lo to high in about 5 minutes ish?  I don't recall exact timing on the lo-high cycles. I can't fire the burner any higher than it already is.
Steamhead, how small a puddle can a puddle be and not create water hammer?The main between the LR rad that heats up ok and the DR rad that doesn't is a 2" line. I'm assuming a 1/2" puddle of cold water would create hammer? No?
Any ideas on using the Mepcos instead of the G2s?

new venting station

@ January 8, 2012 5:25 PM in Location of main vent

any ideas or comments regarding my thoughts that the G2 are sealing up too quick based on just convection from the pipe heating the vents?

Tomorrow I will be installing a venting station just after the DR takeoff.
With regards to you comment about the pressure drop, couldn't I measure that myself by comparing the gauge at the boiler with a gauge at V1?  When V1 just starts to move and showing pressure the difference would be what's shown at the boiler.  No?
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