quick fill to condensate tank???

archibald tuttle

so just took over maintaining a large house with three zone steam (one per floor, two units per floor, haven't even figured out where the thermostats are yet). so this place is big 4500 square feet but its a big house. and it uses hot water in the basement so the lowest radiation is 5 feet above the boiler water line. So, much to my surprise it uses a condensate tank and pump and even more to my surprise, there is 1/2" line with a quick fill hooked up to the condensate tank. there are check valves so i guess maybe - assuming they happen to work well -- that is why it doesn't fill the system and then the condensate pump is operated by a second physical low water sensor/cut-off.

so there is no way to put water directly in the boiler but it appears, unless i haven't found some secret valve somewhere, that the condensate tank is constantly at 12 lbs. i don't get how the condensate can get back into the tank under those circumstances and i can't even figure with 5 ft to play with for A/B distance why they would use a condensate tank anyway.

i will get a picture tomorrow but just wanted to get on hear so anybody who has some early notion of what i'm looking at/looking for could set me straight.

too late for that, started in on the union jack IPA but i'll hold the camera steady tomorrow.

thanks,

brian

Jamie Hall

There's more to this puzzle than meets the eye -- for starters, if that is a condensate tank at 12 psi, there's no way. Fiinish off the IPA and then start tracing pipes!

archibald tuttle

yeah, its flipping my mind so i thought i should get in another kind of tank. maybe the tanks has some kind of bladder in it or something but this half inch line off a standard quick fill goes straight to the tank.

as my friends form delta house said: "my recommendation to you is start drinking heavily"

archibald tuttle

OK sorry. it took me a little while to get back to this, but here is the picture. you will notice a 3/4" copper line attached to a flange on top of the condensate tank and if you follow the line vertically about 4 feet it elbows into the output of a typical quick fill. this is the arrangement i can't figure out. insofar as i can tell tracing the line, the quick fill is just on.

The boiler itself is refilled on low water call by the condensate pump. So I could understand that it might be desirable to have any makeup water occasionally needed enter and mix there rather than cold water line running into boiler. Minor point, but I cannot figure out how the quick-fill can be used as a regulator for this adventure. if it's really putting 12 lbs into the tank, then the water would never drain back from the returns even if the check valves held well and the 12 lbs didn't rise into the system.

I've actually got 38" of head from the lowest return to boiler water level. For the life of me, I don't even see why they used a condensate tank. It is a good sized atmospheric gas boiler. I don't know if it could theoretically evaporate at a high enough rate to hit the low water cutoff before adequate water had drained back by gravity.

of course I don't really think that would happen if run at 'vapor' rather than 'pressure', so the first thing i did was put a vaportrol on it, although i'm desparately seeking one that really works. Honeywell's substitute for the mercury is useless in the vapor region from what i can see.

any prognostications on the what i might actually be looking at here by way of this quick fill hooked up to the condensate take gladly accepted.

brian

JUGHNE

I just went on a ride along to visit a steam boiler and asked the same question you posed. In my case the pump was a boiler feed pump...the boiler calls it to come on. The 12 PSI feed valve is just to protect the internal float operated fill valve from getting wacked by high city pressure. It would fill up just like a toilet tank as needed. and the tank would be under no pressure just like the toilet tank. So my ride along prompted me to read more of Dan's book otherwise I would be more lost than usual. The feed pump might have been installed to compensate for slow condensate return which could be caused by many factors. But the pump would be less callbacks than flooded boiler from fill valve.

archibald tuttle

maybe the condensate tank was put in when they got rid of some gargantuan old coal conversion in favor of a 'modern' atmospheric gas boiler. this is like a twelve section or something. a squat boiler although it takes up a fair amount of acreage. so maybe it doesn't have quite as much water in reserve. although maybe i could just use a low water cutoff set a couple inches above the safety LWCO as a cycle control instead of driving myself crazy trying to get a good vaportrol to operate from 2 oz. to 12 oz.

the thing i can't figure is, if they thought condensate wouldn't come back fast enough and they use a ball cock filled tank to augment supply isn't the system going to get overfilled? because eventually the condensate is going to come back.

i'm thinking that maybe the thing was run at too high a pressure causing trouble getting the condensate back!

just a guess. if the condensate pump crashes and burns i might by pass it and run the thing on low pressure and watch the results for a little while.

thanks for insights from getting to ride along with you to a job or too.

brian

JUGHNE

Page 178 of The Lost Art is the feed pump section, this also clarifies the distinction between cond pump and feed pump. My take on this is that only the bottom quarter of the feeder tank is filled by its own fill valve fed by that 12 PSI auto fill valve. The top 3/4 of the tank is the reserved for condensate return. So the boiler has more water to work with. Without over filling or low water issues. The top 3/4 of the tank can rise and fall without the auto fill coming on.
As far as needing the pump; perhaps the 38" may not be enough height depending the operating pressure of the boiler. From what I read here on the wall most people encounter is that the pressure is usually set to high most of the time. Someone here will want to know what pressure this runs at and of course more pictures of the boiler piping. This sounds like a bit of a complex system with zone valves, traps and hot water heating.

archibald tuttle

complex is putting it mildly. note this other thread on accurately controlling pressures under 16 ozs, or more importantly for present discussion under 28" W.C. and with wide deadband to help limit short cycling.

so that might handle the condensate return/fill tank issues.

meantime, i think i'm just going to eliminate the zone valves (i.e. lock them open) and let anyone's thermostat call for heat and work with tenants on adjusting end valves carefully.

it just seems pointless to zone steam on a boiler that does not have variable fire. everyone i talk to tells me empirical knowledge teaches that the same house heated with steam with thermostats at same setting without zones would save 40% fuel for no appreciable decline in comfort.

i don't know what possessed people to build systems like this. if they had put their efforts into variable fire rather than all kinds of silly bells and whistles to break they would have a got a lot more bang for their buck.

brian

PS - appreciate the distinction of condensate vs. feed pump, but even if the fill function is only to 1/4, I guess the idea isn't really slow return but rather not delivering cold water on the occasions when there has been a loss of water.

so i would imagine that a solenoidic feeder with a restriction so that the feed rate was very low hooked up around or above the operating water level in the hartford loop would allow mixing with condensate in the loop and thus limit cold shock to the boiler.

maybe it would rot the loop a little quicker although one thinks there might be a case for a cooper bottom, but i digress.