Care and feeding of your funky drop header.

Patrick_North

Dear all,

A bit of a follow up, and more questions...

A week or so ago you all offered advice on delaing with a newly, weirdly installed drop header. Instead of having all boiler takeoffs on one end, the equalizer on the other, and all main risers in between, this header (L to R) reads: main riser, boiler takeoff, boiler takeoff, main riser, equalizer.

Smith boiler's lead engineer in such matters essentially said if it ain't broke, don't fix it, that the large 4" header likely made this orientation a non-issue. The installer has said no noise = no problem and is obviously not likely to change his mind. Suddenly it looks like I don't have a leg to stand on. We can't afford to have this redone at our expense, so on to acceptance.

Smith and my installer's insistence aside, I now have huge balancing issues. Previously, separate boilers served the first and second floors - now the "good" main riser (in between the boiler takeoff and equalizer) serves rads on the first floor, the "bad" riser serves the second floor. There's about a 10 degree difference in the two floors with the thermostat (on the first floor) satisfied. I have Hoffman 1A's on all radiators and have dialled back all the first floor rads to next to nothing and taken the flow restrictor caps completely off the rads on the second floor- still not having much of an effect on balance. I've got Gerry Gill and Steve Pajek's venting capacity chart and have determined that Gorton "C's" may be the way to go on the second floor rads (the mains are already well vented- though not maxxed out- with Gorton #2's).

Before I dump even more $$ at the problem, anyone have any better ideas? What about maxxing out the main vent on the slow "bad" main?

Thanks everybody,

Patrick

Jamie Hall

Cheer up

I've seen odder header arrangements (the building I super, for instance, uses the 6" header (steam drum?  collector?  whatever) from a 1920s HB Smith with all but 2 of the original steam connections plugged, giving a boiler takeoff, steam main, long space, boiler takeoff, steam main, then equalizer and Hoffman loop connection, from left to right) and they work OK.  I suspect if you could colour code the steam (what a thought!) you'd find most of the steam from the left takeoff would go to the left main, and most of it from the right to the right main, with very little flow in between.  If the steam is dry enough, don't sweat it.



However.  Your original installation had separate boilers for the first and second floors (I won't ask).  Were they both controlled off the same thermostat?  Or was there a separate thermostat for each boiler?  Were they both running on the same pressuretrol or vaporstat?  Were they interconnected in any way?  How?  I think you can see where I'm going on this: if they were separate, you had two distinct systems (even if they had the same thermostat) and it may be very difficult, if not almost impossible, to balance them without using TRVs.



Before you go there, though, a really quick check: do the second floor radiators see steam at more or less the same moment as the first floor radiators, give or take a minute or two?  If so, playing with the main venting isn't going to help a whole lot, in my opinion.  If the second floor is slow, have you considered vents at the tops of the risers (not radiator vents, but main vents before the radiator valves at the top of the risers)?  That might help.

Patrick_North

Thanks for the condolences!

The house is a rambling old Victorian that once upon a time was an upstairs/downstairs duplex. Thus, there was aboiler for the first floor and a boiler for the second and third floor. Each boiler had its own thermostat and pressuretrol, and each served two mains that went L&R to circle the basement. We didn't have balance problems because there was nothing to balance! Now that we have one boiler we have essentially twice as much main piping as is necessary- a future project will be consolidating these mains so all radiators are served by the same loop.

Currently, my first floor rads get completely hot before the second floors rads are perceptibly warm. The only thermostat (now) is on the first floor. By the time the thermostat is satisfied the second floor is 10 degrees behind, so I'd say they are heating very much slower. Because the second floor has its own mains, I could add more main venting for just these rads. Only about half the second floor risers are accessible (some are in the wall) so venting risers may be hit and miss. I'm hoping that a substantial increase in CFM of the cold rad vents will help- Gorton "c's" versus the current Hoffman 1As. If I have to buy a dozen Danfloss TRV's right now... ugh.

Thanks,

Patrick

jpf321

measurements?

can you provide:

-- measurements of your mains and take-offs and risers? both length and diameter.

-- can you also provide EDR for each rad in the house?

-- lastly the current timing of steam from header branch to each main end?

-- do you currently have main vents?

that data will assist in calcs to balance the system. (the timing is to see if there is improvement after balancing)

Unknown

Vent the Second Floor Main

If I'm reading your description properly it sounds that like the first thing to do is to vent those second floor mains. One, that will get the steam up there faster and two, it will pull some of the steam capacity from the first floor main, helping the balancing.  What type/size vents do you have venting the second floor main now?`

I really find that timing the system helps.  Take time measurements on how long it takes for steam (heat) to get to the end of each of the mains. Then when you make a change, take another timing as this helps you determine whether the change was beneficial or not. 36

It's also not a bad idea to time when steam gets to each radiator (feel the inlet pipe) and how long it takes for each radiator to fill with steam (The vent closing).

 If the venting of the second floor mains isn't satisfactory you can vent the laterals. I've attached a drawing on this.  I would possibly consider this after adjusting the main venting and radiator venting doesn't satisfy your needs. (The Gorton "C"s have about twice the venting capacity of a Hoffman 1A wide open)

As Jamie mentioned, your system sounds fine. It just needs a bit of "tweeking".

- Rod

Jamie Hall

Aargh... I was afraid you were going to say that

That is that the house was once really two completely separate heating systems.



To start with, there may be rather fundamental differences in the ratio of heat loss to radiation in the two systems.  The two systems probably operated at different pressures; almost certainly at different relationships of load to boiler size and firing rate.  Balancing this puppy is going to be very very difficult.  Perhaps not impossible -- but ... but ...  



Very honestly, what I would do, if this were my headache, is to have two thermostats -- one for the first floor and one for the second and third floors.  As I understand you, the first floor has basically one set of mains, and the second and third floors another set.  I would wire each thermostat to a valve on its respective main (make sure these are full port valves), with the end switch on the valves connected in parallel to the boiler, so that if either valve is open the boiler is enabled and fires up.  Make sure that the valves are dripped upstream to the returns!!!



Granted, there will be times when the boiler is oversized rather badly for the system which is "on".  But I would expect that these occasions would actually be rather rare.  Something to look at.  It is possible, too, that it could be downfired to compensate for that.

Patrick_North

D'oh.

Clicked on your image (above) right before clicking "submit" and lost my post! Guess I'll try this again:

Each main (two for the first floor, two for the second) is vented by its own gorton #2. Don't have the dimensions on me, but ordinarily I'd say this is servicable. Of course this has become an out-of-the-ordinary scenario!

I'd guess that under ordinary circumstances, if the mains are vented amply and equivalently, balancing can be handled via the rad vents. I now have 1A's on everything, but there just isn't enough difference between a wide open 1A (on the second floor rads) and an almost closed 1A (on the first floor) to help much. I'm hoping the Gorton "C's" offer enough contrast to the clamped-down 1A's to really affect the balance. They're on their way from pexsupply, so I guess I'll find out soon. If this doesn't do the trick I guess I can add more venting capacity to the "cold" mains. Guessing I should persue this before adding lateral venting, then.

In the meantime, I'll time my mains with the wife, a stopwatch, and the old ai-yi-yi test. I'l report back soon, gentlemen.

Thanks,

Patrick

Patrick_North

Gulp.

Here's hoping the vent maneuvering does the trick- this sounds worse than TRVs! I'll keep you posted.

Thanks,

Patrick

Unknown

Venting

LOL - Jamie - You say "Cheer Up!" and then you drop the "other shoe"! I understand what you are saying though trying to make zone valves work opens up problems of its own with drips etc needed. While I realize you have a lot more experience with these type of systems than I do, I just think that at this point the best thing would be to do is treat them as being like two mains and maximize the upper venting and slow the lower (radiator) venting as necessary. If that doesn't produce satisfactory results then it maybe an idea to move the thermostat to the second floor and use TRVs on the first floor where needed.  Do you see any downside with trying this approach?

- Rod 

Jamie Hall

Not really...

It certainly is worth trying first -- maximizing the venting on the upper floors first, that is.  I would certainly go to big vents at the tops of the risers upstairs -- Gorton 1s or 2s -- in addition to the radiator vents (there is such a thing as venting a radiator too fast).  You can probably hide them somewhere... !  That may help.



The possibility of TRVs downstairs remains, too, and would certainly help with that.



I just have this nasty sneaking suspicion that the upstairs system may have been designed and built to quite a different set point -- different design temperature, etc. -- which may make the whole thing iffy.  Actually, zone valves are not too bad -- the trick is first, to use full port valves (don't cheat here) and second, I like to drip both sides to a wet return, if available.  Think about it...

Patrick_North

Update

OK, I ran some highly unscientific testing. From a cold start, it took nearly 20 minutes to heat the "good" (first floor) main to the point I couldn't keep my hand on the pipe. The boiler switched cycled off and on. At about minute 25, the "bad" (2nd floor) mains heated to about the same degree at about the same time.

Each of these mains has a Gorton #2.

The 2nd floor loop clearly isn't taking on steam as readily. I'll be adding faster radiator vents on the upper floors to compensate for their distance from the boiler, but that seems adequate only if the mains were all heating at the same time to begin with. Shall I assume I need to increase main venting on the cold mains? An extra #2 apiece?

For the record, the boiler is in dire need of skimming, and the vaporstat has proved a dud at very low pressures and is currently set at about 4oz/ 15 oz. No telling the true operating pressure.

Thanks all,

Patrick

jpf321

length of each main?

what is the length difference between the 2 mains? i assume they are both the same diameter. it may be that the steam needs that extra 5mins to travel the extra X feet. my mains are 10ft difference and there is a 2-3min difference.

MAIN 1 = 65ft length@2" and has 182sq ft of EDR and 3.704 CF to vent (rads+pipes)

MAIN 2 = 55ft length@2" and has 189sq ft of EDR and 3.952 CF to vent (rads+pipes)



MAIN 1 end gets hot in ~13mins

MAIN 2 end gets hot in ~11mins



all rads are vented with Gortons according to Gerry Gill's 1oz figures and EDR load. each main has a Gorton #2 at the end. I choose 3mins as desired vent time and I have

2.22 CFM capacity (1.235 CFM needed) on MAIN1

2.40 CFM capacity (1.317 CFM needed )on MAIN2

which is about double the capacity needed for each.

Jamie Hall

Might try

upping the vent capacity on the cold mains only first, and see if you can get steam to both first and second floor radiators a little closer together.  Then to cut down the firing time to heat at the radiators, up the venting on both at once.  20 minutes to heat at the radiator is a bit long, in my humble opinion!



However, I am still concerned that that may not be enough -- the 10 degree differential you cited in your first post still suggests to me that there is a big difference in the design characteristics of the two systems.  If this is so, it may still be necessary to turn the 'hot' (first floor system) just plain off -- TRVs or zone valves -- so the boiler can warm the second floor without overheating the first.

Steamhead

Can you post

the header pic again, and indicate how the various mains connect to it? 

Patrick_North

length of mains

Hmm. A few light bulbs are going on. Maybe.

Remember this header has only two main risers that split (not quite a bullheaded T) to service two mains each. The riser that serves the "cold" mains (on the right in this picture) has one main at 41' and one at 49'. Each of these is vented by a Gorton #2. The riser that serves the "hot" (first floor) mains (on the left in this picture) has one main at 42' vented by a Gorton #2 and one main at 25' vented by a Gorton "D" radiator vent. All of the mains are 2.5"

If you consider each main individually, each of the two "cold" mains take a substantially longer time to fill with steam than the similarly sized "hot" main. But if you consider the cold mains as one unit (they are both served by the same main riser from the header) and the hot mains as a single unit, you can see that the main riser serving the "hot" mains has 67' of main overall, the cold side has 90'. Haven't crunched numbers on air volume/venting ration, but I'd guess it's similar.

My head hurts.

Patrick

 

jpf321

a silly idea but ...

assuming that all mains are fully insulated as shown in the picture, an idea may be to remove insulation from the hot-side...as I said it's a silly idea, but it may help with the comfort balance problem.



i'm also wondering about that horizontal T take-off on the right side of picture to the main that runs out the right side of picture. steam might have a hard time finding that opening as it rushes past  it to straight up to the elbow and then "comes at us" (as per the picture) do all near-boiler pipe fittings heat at the same time? i can imagine the steam having an easier time finding it's way into both of the mains in the background (left side of picture)



just trying to help with some of my thoughts...maybe it will spark more lightbulbs in your own head :-)

Steamhead

I think I see the problem

there is water backing up in the header on the end that feeds the two cold mains, despite the header's size and pitch. The steam velocity is holding it up. This is chilling the steam. It will have to be changed.



When the boiler shuts down after running a while, immediately listen closely (without burning yourself) to that section of the header. I bet you hear gurgling.



How would I fix this? First, remove the 45 and 90 from the section of the header feeding the cold mains, and plug the side of the tee where the riser from the boiler connects. Then remove the ell at the other end where the equalizer connects. Replace this with a tee and pipe from the bull of the new tee to the cold mains- this doesn't need to be 4", just the size of the pipe going into the tee where the cold mains split off (which looks like 3"). Continue with a short nipple off the run of the new tee and tie in the equalizer.

Patrick_North

Aha!

I wondered why the boiler would have cycled on pressure that way. So the boiler fired, filling only the hot main because the cold mains' riser was "clogged." when hot, the main vents on the hot main closed, the pressure dropped, and with it, the water "plug." Now with the hot mains closed for business, the steam's only choice is the cold main which fills about five minues later.

If I understand correctly, this makes a lot of sense. I'll check it first thing tonight.

Thanks!

Patrick

Jamie Hall

never would have thought of that

There is a reason I read the Wall every day.  Every day I learn something potentially (or immediately!) useful!  Thank you!

jpf321

just for my own understanding ..

If I read Steamheads instructions correctly .. it sounds like the new order should be header-right, header-left, hotmains, T with wrap around pipe for cold mains and a runoff for the equalizer.



The purpose of this is to keep steam running in the same direction from the risers and not having 2 risers collide and trying to go in 2 directions? Is this the correct analysis of Steamhead's post?



 I'm just trying to learn from the masters. Thanks

Patrick_North

The water sure is going somewhere...

OK Steamhead, I checked on your theory, and I'm not certain.

When the boiler comes on from a cold start the boiler water level drops to the "low limit" mark when steaming. The boiler then shuts down on pressure with only the hot main remotely hot (about 20 mintues). Now I'm not sure that I heard water rushing back down the cold main riser (what would this really sound like? I imagine not like the sound effect used on beer commercials to signify a long, lusty pour) but I sure heard something. The water level jumped immediately to just above the "normal steam water level" mark- about a three inch jump in the sight glass.

Now I know it's normal for the water level to dip a bit while steaming, but this much? And this is immediate- it certainly isn't condensate trickling back from radiators. How would I confirm this, short of drilling a hole in the header?! For another thing- does 20 minutes seem excessive?

Thanks,

Patrick

Charlie from wmass

Any one out there need a boiler your size?

Perhaps you can make a trade for two smaller boilers?

We may have our first canidate for a modulating residential boiler here Frank? Mason valves and a modulating burner?

Charlie from wmass

Antler venting maybe called for.

You can then put two or three Gorton #2 vents on the cold main.

Steamhead

I think

that would support my theory. It would take that much water to make the level in the glass jump that high that quickly. And you shouldn't hear any noise in the header at all.



If you need another pair of ears on that, I could certainly take the opportunity to check out the upgrade of US 322 thru the Narrows ;-)

Steamhead

That is correct

and for the same reasons you mention.

Patrick_North

Still more to try...

Not waiting for the installer to "get around" to skimming the boiler, so I'm going to do it tonight. I'm sure it's not helping the situation, and with that out of the way (AND the increased venting) it ought to be pretty clear that we've narrowed it down to the header piping.

Here's hoping.

Patrick