1 or 2 cycles per hour for 1 pipe steam

gfrbrookline

I have a now, thanks to New England Steam Works for the mains and some experimenting on my part with various Gortons on the radiators, very well balanced system. My mains and returns are insulated. Would I realize any fuel savings by switching from 1cph to 2cph? I am thinking it would keep the pipes warm and would tighten up the heat swing but am concerned that 2cph would make the boiler run more often but for shorter periods so don't know if I would be saving or not.

Fred

It's more about how much (in fractional degrees) the temp swings before there is a call for heat. I doubt that you will see any noticeable fuel savings but, if you are sensitive to temp swings and notice a quarter to half a degree change (most people really can't) you may be a little more comfortable.

gfrbrookline

I am in a corner brick row house with one side that faces east and cool down faster than the sandwich side so 2cph might make more sense.

KC_Jones

With the eco steam I run 3 and it's blissful.

Jamie Hall

Whichever makes you most comfortable. There will be little difference in fuel use. Of course, with my faithful mercury T87s it's not an issue!

gfrbrookline

I used to complain that my VisionPro 8k would overshoot the setting on half of the building with our new boiler. Once I figured out the main and radiator venting it became very even.

EBEBRATT-Ed

Leave it at 1 cph....Unless you notice it getting cool in between cycles. It's a comfort thing and relates to how fast the building looses heat.

You might have to change it during colder months

HVACNUT

> @Jamie Hall said:
> Whichever makes you most comfortable. There will be little difference in fuel use. Of course, with my faithful mercury T87s it's not an issue!

Its become quite an issue for me. I now need the Hubble telescope to see and adjust the anticipator.

PMJ

I'm with @KC_Jones , 3 is a real sweet spot for steam.

I also agree that open vented I don't think whether 1 or 2 or 3 cycles changes the efficiency much. So I suggest more so temperature swings are smaller.

The only thing I have found that changes the game significantly in both comfort and efficiency is vacuum.

gfrbrookline

So why do so many on here tell people to set the tstat to 1 cph. I have had mine set to 2 cph now for two weeks and it is much more even, no overshoot in any rooms and I don't have any issues with the LWCO adding water. It runs more often obviously but for a shorter period of time, the larger radiators don't heat through but since the heat is even don't see that as a bad thing.

Fred

I would say 1 or two is fine and some even like 3. Mine is set at 1 cycle per hour and my temp swing is not noticeable. I have a 1 pipe system. I don't overshoot the Thermostat either and the fewer cycles certainly means fewer times where you use fuel to push air out of the system and rebuild steam. It boils (pun intended) down to what you are most comfortable with.

gfrbrookline

What I have experienced is at 2 cph the boiler runs more often but for much shorter intervals, since the water and piping don't cool down as much it's probably a wash in fuel cost. I am happy to see the LWCO not adding water on the shorter burns which will help the longevity of the boiler. On 1 cph the LWCO would always add a little water.

Jamie Hall

gfrbrookline said:

So why do so many on here tell people to set the tstat to 1 cph. I have had mine set to 2 cph now for two weeks and it is much more even, no overshoot in any rooms and I don't have any issues with the LWCO adding water. It runs more often obviously but for a shorter period of time, the larger radiators don't heat through but since the heat is even don't see that as a bad thing.

I would say... legitimate differences of opinion, sir, perhaps related to different systems or preferences. Could that be? As it happens, for the main place I care for, roughly one cycle per hour seems to work best (though I still prefer anticipators, which do a better job). For some folks with systems with less size, two might work better. Or even three. No one came down from the mountain with a number...

gfrbrookline

point taken

PMJ

Whatever total run time is required to meet the demand per hour divided into smaller pieces spread evenly apart will make more even heat. More pieces....more even, not negotiable. Whether the larger swings with fewer cycles are "noticed" or not is another matter. They are there and they are in fact larger.

I now run a system that I have set free to do as it wishes with regard to cycles. On all calls for heat the burner fires until either a temp switch at the most remote rad sees steam at its feed pipe or all vacuum in the system is gone, whichever occurs last - plus 2 minutes. If the call is still in place after that the next firing is triggered by that same temp switch opening again which signals all forward steam progress in the vacuum has stopped. The burn then continues to whichever occurs last of the same two things again plus 2 minutes. After the first cold start the last to occur is always all vacuum gone. In this way the cycles adjust themselves according to the demand and keep rads partially full over very long periods providing very even heat. The burn vs wait percentage changes itself according to the demand - mild days will be around 5 minute burns and 15 minute waits, average days will be 8 minute burns and 12 minute waits, cold days get to 10/10. But all on its own it has ended up right around 3cph +/- in all conditions. Right at the time the feed pipes to the rads just start to cool and the vacuum is at its maximum the system fires again and fills right back to where it was last cycle plus a very small amount. It is the fastest delivery of new steam to the rads possible (without a pump) in deep vacuum with no air to push out.

This is without question the most even and most efficient way I have run in what is now a quite long period of experiments. And for this, no PLC control is required. Perhaps the coolest thing about the vacuum is that just at the point it disappears in a new firing the fill level of the entire system is exactly where it was the previous cycle when the burner went off. Monitoring it allows ongoing refilling to partial fill cycle after cycle. Calls go on for hours on average demand days proving the heat is very even. Perfectly even heat would obviously be an endless call.

ChrisJ

gfrbrookline said:

So why do so many on here tell people to set the tstat to 1 cph. I have had mine set to 2 cph now for two weeks and it is much more even, no overshoot in any rooms and I don't have any issues with the LWCO adding water. It runs more often obviously but for a shorter period of time, the larger radiators don't heat through but since the heat is even don't see that as a bad thing.

Because the lower the setting, the longer the system runs. This causes more overshoot and the system stays off longer.

The longer run times help deal with poor venting, balancing and or poor thermostat placement. So, 1 CPH is a safer thing to tell most because it is most likely to "work" on all systems.

I'm guessing some systems, with long runs of piping may need 1 CPH, I don't know. But for smaller residential systems 2 should do fine if everything is set up properly. 3 will also work if everything is perfect.

Yes, 1 CPH "works", but then again, so does manually turning the boiler on and off.

Be warned, when you initially adjust the CPH higher, it will usually cause some issues for a while until it settles in. Such as firing the boiler and then shutting down before radiators even get steam. It'll settle down after a day or so.


Interestingly, Honeywell always said to use an anticipator setting of 1.2 with steam, which also means "no anticipator". 1 CPH is the equivalent.

Fizz

What would be the equivalent anticipator setting on a Honeywell T2280 mercury t-stat to get shorter run time(2cph/3cph)?

ChrisJ

Fizz said:

What would be the equivalent anticipator setting on a Honeywell T2280 mercury t-stat to get shorter run time(2cph/3cph)?

Depends on the current the system draws. It's just a tiny heater that pre-warms the bimetal spring in the thermostat so it thinks the room got warmer faster than it did.

So, start at 1.2 and slowly move it to lower and lower numbers until it seems to behave the best to you. If you get a bunch of short cycles that aren't heating the house, start moving it back until you hit the sweet spot.

Try .8 and see how it does, and then move it a hair towards .6 etc. Very small changes will make a difference.

Fizz

Thanks Chris!

Fizz

My bad! It's a 228D, with anticiipator settings from .18-.8, left to right witn longer inscribed arrow to right.

Jamie Hall

Try setting the anticipator in the middle of its range, and then adjusting it from there.

Fizz

Which way, right is higher settings?

Jamie Hall

Hard to say which way will give you the best results. I'd try the centre to begin with, then if I didn't like it try moving half way to the end in either direction. Makes it worse? Try moving half way to the end in the other direction. And so on. Take your time... it can be a little fiddley to get it right where you yourself, in your own system, want it.

Fizz

Good advice as always, thanks Jamie!

ChrisJ

.8 is the lower setting and .18 will give the most anticipation.

Fizz

Thanks Chris. Moved setting to higher setting, may eventually end-up at .18.

gfrbrookline

We recently had a noreaster and our first snow of the year with heavy winds. I set the tstat to 2cph and installed a combination of G4's and Ventrite No. 1's turned to 3 on the traditionally warm side. On normal days we are within one degree, on stormy days with high winds we used to be five degrees apart or more. With 2 cph we are within one degree on stormy days, so much better.

I am also thinking it must be somewhat more efficient, yes you are heating the water more often, mine is held at 160 since I have indirect HWT off the boiler so not huge, since my pipes are insulated I am not wasting energy reheating the pipes.

gfrbrookline

Update

The temps dropped to the 20's and I had to set it back to 1 CPH because the units furthest away from the boiler were not getting enough steam to heat properly. With 1 CPH we are now heating evenly again.

nicholas bonham-carter

Bfr-your problem probably deserves more main venting, and it’s own thread.
The radiators in the farther area are not getting steam at the same time as the closer ones.—NBC

Jamie Hall

nicholas bonham-carter said:

Bfr-your problem probably deserves more main venting, and it’s own thread.

The radiators in the farther area are not getting steam at the same time as the closer ones.—NBC

Maybe. But there are other possibilities -- such as, how long are these mains? Even fully insulated with maximum venting, anything faster than about 15 to 20 feet per minute for steam travel in a cold main is doing well. If they aren't insulated... it can take twice as long.

This is one of several reasons for the longer, less frequent cycles.

Eastman

I've gotta ask, has anyone ever tried like 6 or 10CPH? What happens?

Jamie Hall

Assuming from a cold start? A number of people have come to the Wall with steam problems which have been traced to having an electronic thermostat set of 6 cycles per hour, which is the usual forced air setting.

Steam (and hot water, but more steam) has a built in time lag from a cold start: it takes time to get the kettle boiling. Several minutes, in fact, for a boiler of any size. So if you are thinking of 6 cycles per hour, that's basically 5 minutes on and 5 minutes off. You'd just barely get steam started when it shut off. Not good. Certainly nowhere near enough time to get steam to the radiators and the radiators warm.

With much shorter cycles, though, you are beginning to get into the territory of pulse modulation of the boiler, and it will begin to behave very much like a smaller boiler -- how much smaller depending on the ratio of on time to total cycle length. This is what happens to any boiler towards the end of a very long run, unless it is very well matched to the load -- it will cycle on pressure at a rate and duty factor such that the average output of the boiler over time exactly matches the load. If you were to run the short cycles at the beginning of the run, however, it would still behave as a smaller boiler, and have difficulty managing the pickup loads in the piping and preheating the radiators.

Eastman

Jamie, crank your system up to 6CPH and make a video.

Edit: I forgot, you don't have a CPH stat hooked up, though. Never mind.

coelcanth

too many cycles per hour in my system just means the boiler shuts down before steam gets up to the second floor

PMJ

3 cph +/- with vacuum in between is really nice. I am approaching radiator conditions similar to a continuous fire. 1200 minute call for heat the other day with the temp at the tstat just not moving. 5-6 minute burns 3 times an hour. Rads maybe 1/4 full max to heat the place at 20F outside over that stretch. Feed pipes to rads always hot. That's all it takes in these systems they are so over-radiated by design. Never meant to be close to full. I see no benefit to filling more than needed for the current demand. I think we can all agree that filling radiators more than needed then backfilling them with air every cycle doesn't make the heat more even.

The change of ongoing uninterrupted rate of condensation in a partially filled system was the whole basis of control in the original system. I am finding that I can control the same way as long as I don't kill it with long off periods and a lot of air.

gfrbrookline

All of my mains and returns have 1" insulation, I have a total of 7 big mouths and 4 G2's so main venting isn't an issue.

When I set the Tstat to 1 cph everything evened out again and everyone in the building is happy. The boiler runs for about 20 min per hour which is actually less than it was in total at 2cph and no unit or room is overheating. As others have said the boiler wasn't running long enough to produce enough steam to reach the radiators that were farthest from the boiler.

Vaporstat is set to 1.5 cut out 8oz cut in subtractive, 0-3 gauge never goes above 1psi.

Some systems run better at different settings, mine obviously runs best at 1 cph. I wish I had a vacuum system but am happy that with maxed out main venting I am no longer cycling on pressure. Thank you @NewEnglandSteamWorks for pointing me in the right direction.

It was worth doing the experiment to see what cph would work best.

Fred

There are a lot of variables that affect how a steam system best performs. The size of the system and distance to the furthest radiators, size and length of mains being a few of them, especially on one pipe systems that don't have some vacuum assist. I'm glad you experimented with your cycles and now you know what works best for your building/tenants. Comfort is what it is about.

Eastman

I am disappointed that 3CPH was not achievable

ChrisJ

Sure..
Except for the fact that even during the longer cycles some rooms are heating more than others and that's not right.

All radiators should start heating together, or close.

Jamie Hall

ChrisJ said:

Sure..

...
All radiators should start heating together, or close.

Nice idea. Trouble is, sometimes basic physics and thermodynamics get in the way...

and as @Fred said, the bottom line is what's comfortable and works.

PMJ

Seems pretty clear that the biggest single trouble with most systems these days is that air gets in the way....at least that is what runaway most of the discussion here is about. The extra effort required to push nearly an entire system volume of air out each and every time the boiler fires just subtracts from the overall efficiency of the delivery system. So now longer burns become the only way to purge air from the far reaches of the system to get some steam there( resulting in longer off periods assuring that you get to start from scratch each and every time). Vacuum, even at low levels, improves both the speed and the eveness of distribution a lot. It is indeed surprising so little effort goes into it.