Thinking about adding a Vaporstat with our Pressuretrolls

cubicacres

We're thinking about adding a 1-16 ounce vaporstat to try and run between 4 oz cut-in and 18 oz cut-out per Dan's recent video, if getting 16 oz/1psi (or similar scale) at the radiators is reccomended with our 100 feet of pipe to the farthest radiaor using 2 ounces for distance + turns.

Does this seem like a good setting to save energy and let it cut off on pressure lower if it doesn't need more than 1 psi or so at the radiators? I think we have .5 psi cut in & 1.5 psi cut out now, so not sure how much energy this will save over time-any guesses on potential savings? And any potential issues if we do this? (and add a pigtail under each pressuretroll, new vaporstat and gauge while we're at it)

ethicalpaul

I doubt you'd be able to even notice a difference.

Do you know how often your current setup cycles on pressure?

What is your radiated EDR vs your boiler's EDR?

STEAM DOCTOR

Cleaning boiler might be first thing to do. Water looks quite dirty.

Jamie Hall

Much as I like vapourstats, if this is a conventional steam system -- not vapour -- they are really unnecessary. Don't bother. It might be worthwhile to add a low pressure gauge, though -- say 0 to 5 psi for a conventional system -- to see what the pressuretrol really is doing.

cubicacres

We're not sure if it cycles off on pressure/low water/thermostat satisfied in the past when we watched it during several cycles, as it's almost always within 1-2 degrees of the room thermostat target temp. each time we observe it during a full cycle. We have 32% pickup factor over the EDR we'd need on design day according to our radiator & pipe measurements we did on install, and have never had any problems heating the building on cold days. We did add a 0-3 psi gauge on the end in the photo to see it moving compared to our city required 0-30 psi gauge & 2 0-30psi scale (I think) pressuretrolls. Can we use our observations on the 0-3psi gauge to determine other adjustments we could be making to increase efficicency?

Regarding dirty water, we did fill the boiler for summer storage, so not sure if that will help with cleaning the gauge glass water if it raises the water level out of the gauge, which seems to get dirty a few times per season. We usually do a cold skim to help drain the full boiler and blow down from the bottom 2 gate valves on each side to lower the water level to the proper amount in the sight glass each fall upon startup. Any other thoughts on water cleaning methods? If it's just a dirty sight glass, I've been reluctant to take it off to clean it.

nicholas bonham-carter

How is your main venting?
Can you get steam up to the upstairs with just a few ounces?—NBC

Jamie Hall

Your 0 to 3 psi gauge will tell you all you need to know -- but you will have to be patient and watch it. A system which is adequately vented and on which the pressure controls are set more or less correctly will behave as follows: from a 0 psi start -- not necessarily cold, but off for a while -- as soon as the boiler starts to steam, the psi will also start to rise. It should, however, stabilize at some rather low pressure -- the exact number isn't important, and will vary with the system, though generally it's on the order of a few ounces of pressure. Then it should hold that pressure, or perhaps rise only slightly and slowly for a time. At some later point, the pressure will start to rise again -- and that is when the pressure control, of whatever flavor, should cut the burner off. If the pressure never stabilizes, then you likely have inadequate main venting.

ethicalpaul

We have 32% pickup factor over the EDR we'd need on design day according to our radiator & pipe measurements we did on install, and have never had any problems heating the building on cold days.

This is a bit nit-picky, but I think it's important to say. For sizing of steam boilers to existing radiation, there is no concept of "design day" or "cold days".

All that matters is the EDR of the boiler compared to the EDR of the installed radiation.

The boiler has no idea how cold it is outside, it has no idea of how leaky the house is. All it cares about is how much EDR is connected to it. Pardon the anthropomorphizing.

Then it should hold that pressure, or perhaps rise only slightly and slowly for a time. At some later point, the pressure will start to rise again -- and that is when the pressure control, of whatever flavor, should cut the burner off.

And to add just a bit to Jamie's excellent description, the reason that the pressure starts to rise again after holding for a time is that the radiators start to become completely full of steam and the radiator vents start to close (assuming 1-pipe radiators).

Once all the radiator vents are closed, if the steam pressure does continue to rise to the point where the pressuretrol activates, that is an indication that the boiler EDR rating is too high for the installed radiation, which is very typical.

But this might take a long time! And note you said here:

We're not sure if it cycles off on pressure/low water/thermostat satisfied in the past when we watched it during several cycles, as it's almost always within 1-2 degrees of the room thermostat target temp. each time we observe it during a full cycle.

This tells me that you must not be cycling on pressure very much. You seem to be saying that the thermostat calls for heat, and then the thermostat is satisfied, probably without the pressuretrol even activating.

People who have a big mismatch in the boiler to radiation EDR values generally are quite aware of it (if they are observant) because a typical call-for-heat cycle might be:

1. call for heat
2. boiler fires
3. pressuretrol kills boiler on pressure
4. pressure reduces
5. go back to #2 and repeat many times
6. Thermostat is satisfied

So if you aren't getting to step 3 but instead are skipping from step 2 to step 6, that's a good thing and a vapor stat isn't going to save you any money (and it might not anyway)

cubicacres

Thanks, we do have a single-pipe system. Main venting was maxed out per our calculations with Gorton & Hoffman main vents, however the long line has a smaller main branch & more radiators, so per Steamhead's advice, we could split that branch to help things, saving a few minutes of run time each cycle since the main vents on different branches/loops close a few minutes (2-3 min.) apart. We've been hesitant to spend the money ($?) for that & use a local contractor who's knowledgable about steam piping, yet

We wondered if slightly less than max venting for the faster main branches (intentionally) might help the steam reach the far radiator on the long loop closer to the same time it reaches the shorter main loop branches last radiators, thereby minimizing total run time of the boiler to satisfy most/all radiators/rooms?

We do see an upward step pattern of pressure on the 0-3psi gauge when the boiler runs. If we assume our cut-out pressuretroll is accurate at, say 2 psi (.5 cut-in +1.5 diff), then should we be able to tell when it hits 2 psi that it's cutting out on pressure vs. low-water vs. room thermostat temp. satisfied? If we could identify what's turning off the burners each time, we could then reduce the cut-out a bit with a vaportstat and see if it works to satisfy the thermostat enough. Also, would a slightly lower pressure for cut-out that works reduce the leaks we see? I think we were able to make new leaks when we ran it on max heat for a while last time we did our whole apartment "leak-watch" with a hand-mirror around all the radiators.

ethicalpaul

should we be able to tell when it hits 2 psi that it's cutting out on pressure vs. low-water vs. room thermostat temp. satisfied? If we could identify what's turning off the burners each time, we could then reduce the cut-out a bit with a vaportstat and see if it works to satisfy the thermostat enough.

It is pretty straightforward to see that it's cutting out on pressure. Just crank up the thermostat to 80 and you'll know that's not satisfied. You'll see the pressure go up and probably hear the pressuretrol click and the boiler will cut out, then when the pressure goes back down the boiler will cut in, no real question.

As far as if it's the boiler getting a low-water cutoff, I hope that isn't happening at all. Is your water level dropping dramatically in your boiler during its firing cycle? That's not good.

I'm confused by "see if it works to satisfy the thermostat enough". Both pressuretrol and vaporstat will keep cutting in and out until the thermostat is satisfied so there's really nothing to worry about there. Neither one will fail to get the temperature up. They will just do it with a different number of cutouts.

Also, would a slightly lower pressure for cut-out that works reduce the leaks we see?

You have leaks? If you have seen them, then you know where they are, fix them Not sure I'm understanding this question.

Jamie Hall

Slightly lower pressure will reduce the leakage, yes. A little. Slightly more may pop some open. However... I've yet to see a leak get less over time.

As @ethicalpaul said, if you have even a suspicion of where a leak is, fix it. Even a relatively small leak can add up to a lot of water -- and a lot of water can add up to a leaking boiler, which is much more of a nuisance than a small leak or two or three here or there.

cubicacres

Thanks. The temp is usually pretty good, so we were wondering if it cuts out after heating 1 degree or so, from the pressure, or stops from low water since the sight glass seems to decrease after running several minutes (from around 50% full to 20% or so, sometimes all the way down the sight glass) & the light for the water feeder goes on ocassionally (we have it set for a delay to wait for the condensate to return so we don't overfill).

With the thermostat always at a good temp, it might be cycling a few times to keep it in a good range of 2-3 degrees from the room target every time we see it on the tekmar's display.

We fixed the leaks when we saw them last time, but after minimal water use for several months, water use increased again. We think new leaks must have occured, but haven't re-checked everything again.

We'll check for leaks again. Any suggestions about identifying them? We used a hand mirror on the radiator supply valves & graphite rope to re-pack the nuts if we didn't replace the valves completely for half of the 22 or so radiators in the building. The mains are insulated, but should we cut the insulation off and watch them as it runs using a mirror similar to the radiator supply valves? And the air vents using mirrors? Or other places?

Is watching each area along the system the way to do it while pressure is building for a few minutes each cycle? That suggests we may only have time to check a few radiators every cycle, and will need to spend a few hours or more to check everything while waiting for the steam demand to come back for the thermostat each heating cycle?

ted_p

cubicacres said:

......
Regarding dirty water, we did fill the boiler for summer storage,....

When you refill the boiler with fresh water for summer storage, you should immediately fire the boiler and bring the water up to steaming temperature, which will drive out the large amount of dissolved oxygen which came in that load of fresh water. If you fail to do this, that load of clean new water will turn bright orange with newly formed rust within a matter of days.

I know, because I made that mistake last year....

We did our annual boiler cleaning cleaning on October 1st, but because the weather was unseasonably warm (the high was 86F that day, and 97F on October 2nd) I told the contractor to put off the combustion tests until the weather cooled off (to keep from driving everyone out of the building). So the boiler never got fired until they came back and did the combustion tests on the 10th of October. By the time they were done, and all that newly formed rust was stirred-up, the boiler water was so orange you couldn't see the red stripe in the back of the sight glass below the waterline.

Live and learn....

nicholas bonham-carter

That decrease in water level when firing is suspicious. Mark the water line in the gauge glass with a clothes pin on the protective steel rod, then fire it until the water level lowers, and then turn it off. Will the water level return to the mark? How long does it take. If it’s a quick return, then it’s a pressure issue, with water pushing up into the returns, and the coming back as soon as the pressure hits zero.
Instead of a vaporstat at the moment, I would install an additional 0-3 psi gauge, so you know what your pressure is.—NBC

cubicacres

We did fire up the boiler to 180F on the skim port using our IR thermometer gun (about 10 minutes) after putting in a steamaster & filling it up to the top of the sight glass level +1 more gallon for summer storage. Hopefully 180F/almost steaming & the tablet is enough to prevent summer rust with the new city water. The sight glass dirt does look kind of orange/brown, so it could be rusty.

We do have a 0-3psi gauge in addition to the city's required 0-30psi, and see it reaching 2 different levels of pressure if I'm remembering correctly (maybe 0.8 first, then up to 1.8 or so?).

With the water meter numbers & observing full cycles, we think the water eventually returns & fills up the sight glass without adding new water, but shutting it off seems like a good way to verify this next time we run it. It seems to shut off around the same time pressure, low water in the sight glass, and thermostat is happy, so that started us wondering what's causing most of the shut-offs first, and if we should adjust anything for it.

nicholas bonham-carter

I’m getting through the main venting phase on 2 ounces, so I know my main venting is generous. If you are venting at .8 psi, I would say your main venting is not adequate.
I had some horizontal returns which were just a few inches higher than the water-level in the boiler, and as the pressure rose, a lot of water would hide in those runs of pipe. When the LWCO cut off the burner, the water returned quickly. Repiping The returns solved everything.—NBC

cubicacres

Thanks, we'll watch the 0-3psi gauge again and try and notice at what psi levels the vents close on each of the 3 main loops/branches. We did max vent with 5-6 gortons on the long loop since it's slowest, but maybe drilling a few more taps for more gortons for the shorter/faster main loops with larger pipe diameters (or using an antler to add more) would help. Short of Steamhead's advice to split the long loop ($$), we're wondering if more venting on the shorter loops makes a difference if we're waiting for the long loop anyway. I think the long loop/main branch is up to 3-5 minutes slower to close vents than the other 2 loops if memory is good from a few years ago.

Jamie Hall

Keep one thing clearly in mind when you are trying to make the various mains equal: the velocity of the steam front. There is a common misconception that the speed with which steam will more through a cool or cold pipe is simply related to how fast the air can get out of the pipe at the other end.

This is simply not true.

The steam front in the pipe will only move as fast as it can heat the pipe at the front, assuming that the air can get out at the other end at all at some reasonable pressure -- say registering an ounce or two at the boiler. Increasing the venting isn't going to change that, once it is at least adequate (that's why you look at the pressure and the way it changes with time).

A smaller pipe, all else equal, will heat faster than a larger one. An insulated pipe, all else equal, will heat faster than a larger one.

(There are some interesting corollaries to this with one pipe steam and radiator venting, but that's for another time).

Bottom line: if the pressure at the boiler is low, and stays more or less constant, more venting is going to look cool -- and that's about it.

gerry gill

My first question is, 'what is the pressure the boiler ACTUALLY operates at'? I would determine this by putting a plastic tube off the drain valve and toss it over a ceiling pipe or beam. Open the drain valve and let the water level equalize with inside the boiler. Mark the spot with a bread twisty, and run the boiler for an hour and watch how high the water gets pushed up the tube. 1-3/4'' for each ounce. Then i would decide on a vaporstat based on my observations.

Jamie Hall

What would be really interesting, @gerry gill , is to put a manometer at the end of the steam main, to see how pressures vary there. I've done a variation of that with Cedric -- measured the pressure at the main vents (end of the dry returns, at the Hoffman Differential Loop) and … it's possibly as much as half an inch of water, and stays that way. The pressure rise which shuts off the vapourstat -- eventually -- is from the traps closing. If it weren't for the vents needing to be there for the proper operation of the loop, I might just as well have an open pipe.