Help me tune-up my single-pipe counterflow system!

AaronH

Just bought a house in central NJ with a Weil-Mclain SGO-3/Beckett AFG oil burner. Two stories, 1400sq ft, 8 radiators (but two are shut off... another story).



Seems to be heating OK - but I want to make it better. I just installed a 0-3psi gauge and futzed with the pressuretrol this afternoon and changed a few sketchy air vents.



Before I worked on the system, it was cutting out around 3.5-4psi according the to 0-30 gauge. Now I have it set to:



Cut Out: 2.25psi

Restart/Cut-In: 1.0psi. The system pressure drops to 0.75psi before it goes back up.



The initial burner cycle to get from the call for heat (house at 66 degrees) to 2.25psi was 15 minutes. Each subsequent cycle was 2 minutes, 25 seconds, or 2 minutes 15 seconds of burner-on time because I have a 15 second delay to startup. Total run time to get the house to 69 degrees was 43 minutes, it is about 40 degrees outside.



OK - so here are my questions:

1) Is the cycle time too short for the burner at 2 min 15 sec? Can this damage the burner? Is it inefficient?



2) Should I change those pressure values?



The house seems to heat MUCH more evenly with the lower pressure. But can I make it better??

nicholas bonham-carter

counterflow tuneup

locate your main vents, and post some pictures and info on them. they will have to be at the ends of the main. if there are none then a big radiator vent [gorton d] on the end radiator may work, but best is main vents on the main.

with adequate main vents and a properly sized boiler, the back-pressure of venting should be 2 ounces or less during the first couple of minutes firing from cold. a vaporstat would give you more reliable low-pressure operation, but improve the venting first.

lets see some pictures of your piping above the boiler. looks like copper, which could be a problem in the future, but more important, have they kept the full diameter from the boiler tapping, or is there a reducer?--nbc

AaronH

Main Vents... What Main Vents??

Thanks for the reply... Oy... the piping above my boiler needs to be redone. Yes it's copper and of course it's not correct (there's a laundry list of sins here), and to make matters worse: its got a small leak!



But I'm trying to get away from redoing it yet - I want to make that a project for this summer in case it takes longer than 8 hours, which I know it will if I do it myself.



There are no main vents on this system. The boiler is in the center of the house, with a 16ft 2" main going to the back of the house (3 radiators) and a 20ft 2" main going to 5 radiators in the front of the house. Pipes are not insulated, but 1" insulation has been ordered and should be here soon!!



Here's a pic of the termination of the front main. How could I add vents? Can I just drill and tap the pipe for a 1/4" NPT for say a Gorton D?

Jason Quinn

Lower the pressure

Try to cut-in at .5 and cut-out at 2 psi and see how the system runs. The water in the gauge glass in the picture looks very dirty. You will not get quality, dry steam with dirty water like that. You can search this site to learn how to "skim" the boiler in order to clean the water. As NBC mentioned, check your main vents as well. A 2 minute 15 second run time is short and inefficient. Is your thermostat adjusted/set up for steam heat? Many come set up for hot air systems out of the box. When the system shuts off, is the thermostat satisfied? Is it shutting off on pressure? Low water?

AaronH

Back to basement I go...

I will lower the pressure further. The system ultimately does satisfy the thermostat.



What should I be looking for in terms of run times for the burner? The short cycling was from the pressuretrol cut-out/cut-in to maintain the set range.



The thermostat is a Hunter digital/programmable. I have it set for a "wide" cycle, if it's set for 68, the unit calls for heat when the temp drops to 67 and then shuts off when the temp reaches 69.

Jason Quinn

I would

prioritize adding main vents and cleaning the water. Yes, you can drill and tap the pipe to add vents. You should also read the thermostat manual to see if there is a specific adjustment for steam heat.

Jamie Hall

Tapping iron

it can be done -- provided you really know what you are doing.  And it would be the best way to add vents.



Another approach, though, to adding vents would be if the radiators at the ends of the mains have unions and have elbows leading to them.  The elbow from vertical to horizontal could be replace with a T, and main vents added on the top of the T.



If that burner cycle is on pressure, as you indicate, it should not be a problem for the burner.  It may be that more venting will help it -- but probably not.  It is more likely that the boiler is somewhat oversized for the radiation (this is very common!) in which case the only options are to live with it or downfire the boiler, if you can.  Whatever, it doesn't sound bad to me.  Could it be better?  Sure.  Lots of things could be.  Would it be easy to make better?  Probably not.  Is it hurting the burner?  Shouldn't be.  Is it hurting your efficiency?  Yes, but not that much.

Mike Kusiak_2

Shut off radiators?

You mentioned that two out of a total of eight radiators were shut off. This might explain your short cycling. If sized properly, the boiler would have been chosen on the basis of the EDR of the eight radiators, but now you only have six being used. This would imply that the boiler is generating about 25% more steam than the remaining radiators can condense. Consequently, the pressure rises quickly and the burner shuts down via the pressuretrol until the condensing can catch up.



What's the deal with the two radiators not being used? If they were operating, your short cycling would most likely be much less of a problem

AaronH

Radiators off because:

Short story: One had killer water hammer, one is currently overpowering the t-stat.



Long story:

The upstairs bathroom radiator is is off because the pipes leading up to it were generating an awful water hammer whenever the system would build pressure (about 10 minutes into operation). The piping to the radiator is cast iron from the rear main out to the side of the house, then switches to 1" copper that runs up the exterior wall of the house, makes a 90 degree to go horizontal under the bathroom floor, then makes another 90 into the radiator. It might make another 90 under the floor - but I don't know for sure.



There is no valve on the radiator, so I plugged the vent hole by turning the air vent upside down. It silenced the system quite nicely - and we could finally sleep through the night!! We have an electric wall heater in there (which is amazing for early morning showers), so although not ideal, not having the radiator in there is livable.



The second radiator that is off is in the living room, which has another radiator in it, and the thermostat. With both radiators on, the thermostat would cut the boiler off too soon and leave the rest of the house about 2 degrees below the living room. Until I can move the t-stat (hopefully this week) - the unit stays off and the house is relatively even.

nicholas bonham-carter

moving the thermostat

the honeywell prestige appears to have a wireless temperature sensor, which is easier to move around, and the visionpro thermostat has the option of a wired sensor, which places the controls within easier reach, in a more protected location.

both are available from pex supply.

i think that a reduction of pressure and better air venting will bring the killer water-hammer to justice! remember, the larger size of pipes in a counter-flow system holds more air to be allowed to escape with negligible back-pressure.--nbc

AaronH

Help me size some main vents please

I want to add main vents to the system. Here are my thoughts:



Front Main:

Vent will go where the 2" pipe necks down to 1 1/4" pipe (turns into runout for last radiator). I can change the reducer to a T, and add the vent on top. This would be about 26' from the boiler, and located in the basement. The challenge is that there is only 4.5" of clearance between the subfloor and the top of the 2" main.



Rear Main:

This main goes through a teeny-tiny crawl space, so I'm thinking of adding the main vents at the top of the riser (2nd floor) that's connected to the very end of the main. I got this idea from page 118 of Lost Art of Steam Heating where Mr. Holohan describes Frank Gerety's master venting approach.  This would be about 14' of 2" pipe, and 10' of 1" pipe.



What size vents should I use? Since the rear vent will be in a living space, noise of the vent is important.



Thanks!

nicholas bonham-carter

adding vents

i would get the parts with which you plan to replace that reducing bushing/coupling first, and see if they will fit without shortening one of the pipes on either side. you will need a union somewhere, i would think. a "menorah" setup is best as it enables you to add more vents as needed.

now i see you have a headroom problem, so it might be better to "measure twice, order once".

you could try a menorah of gorton d's on those end/top of line radiators [each rad could support 3]. normally we don't like venting the radiators too quickly, for fear of excessive condensate formation, at start-up; but in your case, the options are somewhat limited, at this time of the year. maybe some different valving will enable the vents to be put on the riser top, in place of the current valve.

you can never over vent a main, and the lower the back-pressure the more quiet.--nbc

Jamie Hall

Good heavens

I'm not a bit surprised that that upstairs radiator had killer water hammer -- if anyone on the Wall is looking for directions as to how to pipe a radiator to create water hammer -- say for a demonstration, or possibly to annoy the neighbours -- they've just found it.



And it's not going to be fixable without completely repiping that radiator.  That 1" copper up the side of the house guarantees hammer, regardless of whatever repitching one might do.



Good grief.



On the other hand... is that the last riser on that main?  If so, since it is useless for heat, you might consider cutting it and putting a main vent on it, down in the basement.  Be easier than tapping that main.

AaronH

That's not the hammering beast...

Jamie,



Thanks for the reply. Fortunately that radiator does not hammer one bit. It's 1" Pipe, but it's iron, and it runs outside the wall - inside the kitchen below. That radiator gets nice and hot, quietly, with an older Hoffman 1A set on #3.



Since it is the last riser on the rear main, that's where I was thinking of adding a main vent. Get a reducing T, close nipple and straight radiator valve and the vent going vertical on the T. Make sense or should I try a different tack?

Steamhead

I'd simply

get a couple Gorton D vents, drill and tap the side of the mains for 1/8" pipe and screw them in. With those short mains you don't need more capacity than that, and this is the easiest way to do it. This will also sidestep your height issues.



Locate your vents at the ends of your mains, rather than the risers, so all the radiators have about the same runout and riser lengths. This will help bring the system into balance. The one in the crawlspace, if inaccessible, might need its vent on the riser, but in that case you can drill and tap the riser itself below the ceiling.

AaronH

Sides or Top?

Hmm... So perhaps a Gorton 1 on each main is too much? Can you have too much main vent?



On another/related note - is tapping the main on the side a good idea because of the condensate return?



I've done quite a bit of tapping in both mild and stainless steels, but never cast iron. What should I watch out for? Also - do I need to watch out for chips going into the main?

AaronH

New cycle times... after some tweaking

Did a bunch of work on the system today, including replacing the metal strap hangers with really nice cast iron rings/allthread/cast joist brackets - and then insulating most of the main with 1" thick fiberglass.



My cycle timing is now:

Burner On: 0.5psi on - 2.0psi off: 3:23

Burner Off: 2:12.



I also moved my thermostat and now have all but one radiator on! I did some EDR calculations:

Current setup (w/problem radiator OFF: 253 

Max EDR (w/problem radiator ON): 281



I'm waiting on a few more parts before I add my main vents. Can't wait...

Mark N

Pressure

Aaron



Does this boiler cycle on pressure every time it runs?

The boiler is slightly oversized but not bad. Maybe next time you get it serviced see if they can downfire it. I have a system that is about the same size as yours. Mine runs at 1oz. pressure or less. Cycling off and on on pressure until satisfying the Tstat isn't the most efficient way to heat the house.