Anti-short cycle timer

rorylane

I have a slightly oversized boiler. On a call for heat it will short cycle on pressure after the initial 5-10 min. burn. Was going to install an ICM206 delay on break timer after the vaporstat to hold it out for another 5-10 before it can fire again. The problem I ran into is that I can't seem to figure out how this thing is wired... I set up a test station with a spare 24v transformer. Wired up to terminals 3 and 2, 1 and 3 have continuity. Switch closed. When I take away power, no continuity between 1 and 3. Switch open. When I reestablish power though there is no delay... Instant closed. Is there a flaw in my method or did I get a faulty timer?

nicholas bonham-carter

What thermostat are you using? Is it configured properly for steam?
What main vents are in place, and how many ounces of backpressure are showing after the initial burn?
Can you have someone downfire the boiler?—NBC

acwagner

I looked at your older post and it sounds like you have decent main venting. Cycling on pressure after 10 minutes sounds more like a massively oversized boiler not a slightly oversized boiler to me.

I can't help on the wiring for that device. But, I have a timer on my boiler to help when recovering from setbacks. This is the one I have:

https://www.galco.com/buy/Macromatic/TR-6512U

Have it in series with the thermostat, and use it to modulate the burner based on time.

Jamie Hall

Um... why? Before you add a timer, be sure that you have really analysed why you need it, and then if it is the best way to handle the problem.

First, if your boiler is reaching set pressure in 5 to 10 minutes, it is either wildly oversized or seriously undervented -- or both. Both of these possibilities need to be checked, as one can be managed by a timer -- though it isn't the best way to do it -- while the other can't be, properly. To check the boiler for oversize, simply add up the EDR of the radiation to which it is connected, and compare that to the rating of the boiler if the boiler has a range of ratings (many do), find out from your service technician what your boiler is actually firing at. If the two match fairly well -- the load on the boiler reasonably close (say within 20%) to the output of the boiler -- there is no point in reducing the boiler's effective output, which is what a timer would do. At that point, check the venting.

But let's suppose that your boiler is significantly mismatched to the radiation. Most are, after all, although the degree of mismatch may not be that bad. Clearly some means has to be found to adjust the boiler's output to the load placed on it by the system. (Note that this is very different from the demand placed on the system by the structure! That should be handled by the thermostat, or in much larger systems by some other means which relates structure load to environmental conditions).

My own control philosophy (and others differ) has been, for years, to try and determine for any system I am working with what parameter, or parameters, is most closely related to the thing which needs controlling, and use that as the control parameter. A trivial and homely example would be the water level in the tank of a flush toilet. The level of water in the tank, to function properly, needs to be at a specific point. The thing that needs controlling is the amount of water fed to maintain than level. So... control parameter is water level, and I put a float valve in the toilet tank. In principle, I could also determine the average time between flushes and set the water feed rate so that the tank was just full enough at the next demand. Or I could determine the average number of uses per day, and set a timer to turn the water on to the tank that many times per day, with so and so long a run per dose. A small amount of though will show that those two latter concepts just aren't going to work.

What easily measured parameter on a steam heating system is most closely related to load vs. supply? Pressure. If the load is greater than the supply, the pressure will be low and dropping (quite fast!). If the supply is greater than the load, the pressure will be high and rising (also remarkably fast). So clearly the thing to do is to determine what pressure the system operates at at full load. In most residential systems this will be on the order of half a pound per square inch. Some -- vapour systems -- it will be less (a few ounces). Some it may be more. Then having done that simply control the system so that the pressure doesn't rise either much above -- or much below -- that value. In most residential systems, again the gadget to do that is a vapourstat -- either 0 to 16 ounce or 0 to 4 psi, as appropriate. Set it to turn the boiler off when the pressure is in excess, indicating the supply has gotten ahead of the load, and turn on when the pressure is low, indicating that more supply is needed.

Done.

Let the burner controls worry about things like minimum off time between firing (in oil burners, there is one, controlled by a post purge and pre purge timer).

rorylane

A little history... I had a Burnham 5008B when I bought the house, at 1367 sq ft EDR I knew it was oversized. I replaced that boiler a couple years ago with a WM EGH-105 at 977 EDR. I sized it for the 1000 sq ft EDR of rads that I have but not all of these are in service yet. Trust me, plenty of venting... The house is a continuous remodeling project with balance issues that I control right now with radiator valves, but long story short the load is smaller right now than it will be in the future. The short cycling comes in when it’s colder than about 15F out. Vaporstat is set to about 10 ozs. When the burner shuts off it drops below cut in almost immediately... this is where I thought I’d delay the burner coming back on while the rads are still hot to cut down on CPH. Thermostat isn’t close to any rads so it takes awhile to satisfy the call for heat when its really cold out. The timer idea was meant to reign it in a bit until I can install rads which will address the balance issue. At that point my connected EDR will align more closely with what the boiler is rated for.

ChrisJ

The timer makes sense, it allows the radiators to dissipate some heat before firing again. Obviously if they aren't taking steam they don't need it, right?

I don't know how exactly your boiler is wired, but here's the basic idea.

The timer looks like it needs a common but whether or not the boiler's common needs to run through it or not I don't know. There's a good chance that connection isn't needed.

https://www.icmcontrols.com/documents/ig_LII35-1.pdf

Jamie Hall

Ah... if the pressure is dropping, they're taking steam. If the pressure is 0 or close, they need more steam...

pecmsg

Smaller boiler or more emitters.

Any chance that boiler can be down sized?

rorylane

> @ChrisJ said:
> The timer makes sense, it allows the radiators to dissipate some heat before firing again. Obviously if they aren't taking steam they don't need it, right?
>
> I don't know how exactly your boiler is wired, but here's the basic idea.
>
> The timer looks like it needs a common but whether or not the boiler's common needs to run through it or not I don't know. There's a good chance that connection isn't needed.
>
Yeah, this is how I wired it with my test transformer, I just don’t get any kind of delay on break...

rorylane

> @Jamie Hall said:
> Ah... if the pressure is dropping, they're taking steam. If the pressure is 0 or close, they need more steam...


I get what you’re saying Jamie. I just figured that I’m still benefitting from a lot of hot cast iron for awhile after the steam pressure subsides.

pecmsg

Those timers cannot handle much if any load. It sounds like the boiler is cycling in the primary control, a relay MUST be used!

ChrisJ

rorylane said:

> @ChrisJ said:

> The timer makes sense, it allows the radiators to dissipate some heat before firing again. Obviously if they aren't taking steam they don't need it, right?

>

> I don't know how exactly your boiler is wired, but here's the basic idea.

>

> The timer looks like it needs a common but whether or not the boiler's common needs to run through it or not I don't know. There's a good chance that connection isn't needed.

>

Yeah, this is how I wired it with my test transformer, I just don’t get any kind of delay on break...

That's strange.
The center terminals look like they're just a jumper, but the outside ones should stay open.

ICM's tech support is fantastic. I've called them with questions and they helped me even though I'm not a contractor. I'm using their fan controller on my A\C and had some questions a while back.

I'd call them and talk to them about it. Maybe bad part out of the box? Doubtful but anything is possible. @pecmsg could be right, you may have overloaded it and damaged it.

ChrisJ

Jamie Hall said:

Ah... if the pressure is dropping, they're taking steam. If the pressure is 0 or close, they need more steam...

If the radiators cannot take enough steam to keep pressures reasonable, and the space is being heated enough, they need a rest in my opinion. A nap.

My Ecosteam is setup to shut the boiler down for 10 minutes if I hit 8" WC. This is because, in theory if 5 TRV's are totally closed it could happen in very cold weather.

rorylane

@pecmsg, I’ll have to check amperage on this application, I planned on putting this in line after the vaporstat.
I’ll call up ICM if I get time, maybe they can shed some light on this.

rorylane

@ChrisJ I was reading about Ecosteam control, what I’m trying to acheive sounds like the “Hold” state described for that system. Why can’t I find more info about Ecosteam? Sounds amazing...

JUGHNE

Your boiler may have an isolation relay on it. If so then perhaps put the timer on the tstat side of that relay.
In the control/vaporstat circuit you have the load of damper motor, ignition module and gas valve.

I have used that delay in the past and the ones with the adjustable times were the first to fail. FWIW

I have had good luck with the MARS 32382, (USA BTW) though it is fixed at 5 minutes delay on break. Wired the same, looks the same without the adjustment. Probably made by ICM
There might be a 10 minute version.

24 vac applied to 2 & 3 will close 3 & 1 immediately.
break the 24 and reapply and wait your time out.

2 is just common from the transformer and to the load and I believe the relay needs it for operation.

pecmsg

JUGHNE said:

Your boiler may have an isolation relay on it. If so then perhaps put the timer on the tstat side of that relay.
In the control/vaporstat circuit you have the load of damper motor, ignition module and gas valve.

I have used that delay in the past and the ones with the adjustable times were the first to fail. FWIW

I have had good luck with the MARS 32382, (USA BTW) though it is fixed at 5 minutes delay on break. Wired the same, looks the same without the adjustment. Probably made by ICM
There might be a 10 minute version.

24 vac applied to 2 & 3 will close 3 & 1 immediately.
break the 24 and reapply and wait your time out.

2 is just common from the transformer and to the load and I believe the relay needs it for operation.

The OP needs to delay the Vapor stat side not the t-stat!

Jamie Hall

rorylane said:

> @Jamie Hall said:

> Ah... if the pressure is dropping, they're taking steam. If the pressure is 0 or close, they need more steam...





I get what you’re saying Jamie. I just figured that I’m still benefitting from a lot of hot cast iron for awhile after the steam pressure subsides.

This is true. And, if your thermostat doesn't compensate properly for it, that will cause an overshoot -- which could be significant. But that's the thermostat's job, and it should shut off the heat in time so that the remaining heat in the radiators will bring the space to the thermostat setting.

I guess I am just oversensitive, perhaps, to mixing control parameters... for the timer controls, if the boiler is simply too big for the radiation, it is one way -- though not sensitive to any of the actual operating factors of the system -- to compensate. I just prefer to control a system variable with some parameter which is actually related to that variable.

JUGHNE

Pecmsg, why not the stat side?

Also some stats have a time delay that prevents short cycling not only in cooling but in heating. Not sure if adjustable out to 10 minutes. Don't recall the model at the moment.

coelcanth

why set the vaporstat to cut out at 10oz ?

i know why normally we want to run at lower pressures,
but in your situation, where your radiation is temporarily undersized, why not just bump up the operating pressure a little bit until you are satisfied ?

if you artificially extend the call for heat with a timer that bypasses the pressure control, the pressure is just going to rise anyway, right ?

rorylane

Thanks for confirming the terminal functions @JUGHNE. I got the adjustable time model so I could play with it a little, good to know that may be a weak point. While I like the idea of an advanced granular control system like a full blown PLC setup, for now I had wanted to keep it simple.

rorylane

> @coelcanth said:
> why set the vaporstat to cut out at 10oz ?
>
> i know why normally we want to run at lower pressures,
> but in your situation, where your radiation is temporarily undersized, why not just bump up the operating pressure a little bit until you are satisfied ?
>
> if you artificially extend the call for heat with a timer that bypasses the pressure control, the pressure is just going to rise anyway, right ?

The cut out is set to 10 oz because that’s all I need to fill the furthest rads in the system. I figured building additional pressure is a fuel waste. This would result in a longer burn, but I’m trying to be more efficient with this setup. (Aren’t we all!) I’m not trying to extend the call for heat, just trying to prevent the system from cycling a bunch to maintain pressure at that 10 oz for the entire duration of the call for heat. Since the rads are already hot, trying to let the pressure ebb and flow a bit more. In some situations the call may be satisfied before a second burn is initiated.

pecmsg

JUGHNE said:

Pecmsg, why not the stat side?

Also some stats have a time delay that prevents short cycling not only in cooling but in heating. Not sure if adjustable out to 10 minutes. Don't recall the model at the moment.

Does the T-stat run in series with the vapor stat? then fine, if not the delay will be closed every time the vapor stat opens!

Jamie Hall

rorylane said:

> @coelcanth said:

> why set the vaporstat to cut out at 10oz ?

>

> i know why normally we want to run at lower pressures,

> but in your situation, where your radiation is temporarily undersized, why not just bump up the operating pressure a little bit until you are satisfied ?

>

> if you artificially extend the call for heat with a timer that bypasses the pressure control, the pressure is just going to rise anyway, right ?



The cut out is set to 10 oz because that’s all I need to fill the furthest rads in the system. I figured building additional pressure is a fuel waste. This would result in a longer burn, but I’m trying to be more efficient with this setup. (Aren’t we all!) I’m not trying to extend the call for heat, just trying to prevent the system from cycling a bunch to maintain pressure at that 10 oz for the entire duration of the call for heat. Since the rads are already hot, trying to let the pressure ebb and flow a bit more. In some situations the call may be satisfied before a second burn is initiated.

Could I ask how long after your burner shuts off does the pressure take to drop? For Cedric the pressure drops from 7 ounces (the current cutout) to 3 ounces (the current cutin) in about 30 seconds (and no, there are no leaks). Condensation in the system pulls the pressure down pretty fast! So my vapourstat plus the post purge/pre purge time delays do a pretty good job of holding the pressure where it needs to be.

ChrisJ

Jamie Hall said:

rorylane said:

> @coelcanth said:

> why set the vaporstat to cut out at 10oz ?

>

> i know why normally we want to run at lower pressures,

> but in your situation, where your radiation is temporarily undersized, why not just bump up the operating pressure a little bit until you are satisfied ?

>

> if you artificially extend the call for heat with a timer that bypasses the pressure control, the pressure is just going to rise anyway, right ?



The cut out is set to 10 oz because that’s all I need to fill the furthest rads in the system. I figured building additional pressure is a fuel waste. This would result in a longer burn, but I’m trying to be more efficient with this setup. (Aren’t we all!) I’m not trying to extend the call for heat, just trying to prevent the system from cycling a bunch to maintain pressure at that 10 oz for the entire duration of the call for heat. Since the rads are already hot, trying to let the pressure ebb and flow a bit more. In some situations the call may be satisfied before a second burn is initiated.

Could I ask how long after your burner shuts off does the pressure take to drop? For Cedric the pressure drops from 7 ounces (the current cutout) to 3 ounces (the current cutin) in about 30 seconds (and no, there are no leaks). Condensation in the system pulls the pressure down pretty fast! So my vapourstat plus the post purge/pre purge time delays do a pretty good job of holding the pressure where it needs to be.

I'm assuming the object here isn't to allow pressure to drop.
It's to allow the cast iron to cool down and dissipate some of it's stored heat.

Cool radiators can use steam faster than saturated ones.

This is why the Ecosteam has it's delay option.

ChrisJ

rorylane said:

@ChrisJ I was reading about Ecosteam control, what I’m trying to acheive sounds like the “Hold” state described for that system. Why can’t I find more info about Ecosteam? Sounds amazing...

Only a few were made sadly.

rorylane

30 seconds sounds about right. The old system was running at 2psi which took a little longer to pull down. @ChrisJ, where can I find more info on Ecosteam?

rorylane

@ChrisJ, I think we posted at the same time... Too bad about Ecosteam, looked promising.

JUGHNE

Pecmsg, yes you are right. tstat would stay closed holding the isolation relay closed. Vapor stat would be the controling factor at that point. So another isolation relay if the delay relay could not handle the current load? Thanks for the correction.

KC_Jones

rorylane said:

@ChrisJ, I think we posted at the same time... Too bad about Ecosteam, looked promising.

I have one too, and it is quite awesome. It is sad it didn't catch on.

rorylane

> @KC_Jones said:
> (Quote)
> I have one too, and it is quite awesome. It is sad it didn't catch on.

Does the software exist anywhere? For me the hardware would be the easy part.

Jamie Hall

A minor thermodynamics reminder...

The only heat a steam radiator can radiate -- regardless of its temperature -- comes to it by means of the steam which is condensed inside of it. The iron cannot provide any heat which isn't brought in from outside. If you need heat from a radiator -- for instance, the thermostat over in the corner is looking for blankets -- you need steam being provided to the radiator. Which means the boiler is firing. If the thermostat is happy, you turn off the boiler. If the boiler has gotten ahead of the radiator, you need to turn off the boiler briefly to let the radiator catch up (in many many ways an ideal system would have a modulating burner -- high subsonic pulse width or analogue -- controlled by a device which directly measured whether the boiler was producing steam as fast as, but no faster than, the radiator was using it -- pressure is the simplest one)(this also ignores systems where you modulate the heat output of the radiator by modulating the condensing temperature by a controlled vacuum -- but you still need to modulate the boiler output).

The only problem with the bad old days when we had coal fired boilers with the draught controlled by very sensitive pressure measurement of the steam was that the efficiency, off peak, was horrid... In principle, modulating gas burners such as are used in mod/con hot water practice could be used (I'm not sure why they aren't...) with sensitive pressure measurement as the control. The best we can do with oil (so far!) is pulse width, with the off cycle kept as short as possible (usually limited by burner shut down/start up cycle characteristics), again controlled by pressure.

(Further obfuscation: if you really wanted to get fancy, you could add to a two pipe system a very reliable vacuum pump with the vacuum level controlled by an outdoor condition (not just temperature) set point algorithm, and a fully modulating burner controlled either directly by the outdoor set point algorithm or by simply maintaining the algorithm's pressure set point directly. Could it be done? Sure. How would it compare with the reliability and maintainability of a simple thermostat/vapourstat/oil burner system? Crickets... Would the efficiency be higher? Probably, slightly.)

All this, of course, assumes that you want to be able to use the full output of the radiation -- and as close to the full output of the boiler -- at least part of the time.

KC_Jones

rorylane said:

> @KC_Jones said:

> (Quote)

> I have one too, and it is quite awesome. It is sad it didn't catch on.



Does the software exist anywhere? For me the hardware would be the easy part.

I have no idea, even if it did I am not sure if it would be given up for free since it's intellectual property. The creator put a lot of work into it.

ChrisJ

Jamie Hall said:

A minor thermodynamics reminder...

The only heat a steam radiator can radiate -- regardless of its temperature -- comes to it by means of the steam which is condensed inside of it. The iron cannot provide any heat which isn't brought in from outside. If you need heat from a radiator -- for instance, the thermostat over in the corner is looking for blankets -- you need steam being provided to the radiator. Which means the boiler is firing. If the thermostat is happy, you turn off the boiler. If the boiler has gotten ahead of the radiator, you need to turn off the boiler briefly to let the radiator catch up (in many many ways an ideal system would have a modulating burner -- high subsonic pulse width or analogue -- controlled by a device which directly measured whether the boiler was producing steam as fast as, but no faster than, the radiator was using it -- pressure is the simplest one)(this also ignores systems where you modulate the heat output of the radiator by modulating the condensing temperature by a controlled vacuum -- but you still need to modulate the boiler output).

The only problem with the bad old days when we had coal fired boilers with the draught controlled by very sensitive pressure measurement of the steam was that the efficiency, off peak, was horrid... In principle, modulating gas burners such as are used in mod/con hot water practice could be used (I'm not sure why they aren't...) with sensitive pressure measurement as the control. The best we can do with oil (so far!) is pulse width, with the off cycle kept as short as possible (usually limited by burner shut down/start up cycle characteristics), again controlled by pressure.

(Further obfuscation: if you really wanted to get fancy, you could add to a two pipe system a very reliable vacuum pump with the vacuum level controlled by an outdoor condition (not just temperature) set point algorithm, and a fully modulating burner controlled either directly by the outdoor set point algorithm or by simply maintaining the algorithm's pressure set point directly. Could it be done? Sure. How would it compare with the reliability and maintainability of a simple thermostat/vapourstat/oil burner system? Crickets... Would the efficiency be higher? Probably, slightly.)

All this, of course, assumes that you want to be able to use the full output of the radiation -- and as close to the full output of the boiler -- at least part of the time.

Are you suggesting the Ecosteam isn't reliable?
Mine has never welded it's contacts shut............Just saying.

My radiators continue to delver heat for a good 30+ minutes after the boiler shuts down. 212F is quite a bit above ambient and there's a good amount of "flywheel". Mass stores energy and even my small system has somewhere around 4000 pounds of iron if memory serves. In fact, the entire point of the Ecosteam is to compensate for this flywheel effect. Both during normal operation and during recoveries so there's no overshoot.

I've seen where my thermostat is never satisfied, but the Ecosteam times things just right so there's literally no temperature swing. Boiler fires and heats the radiators X amount and shuts down and the system coasts.

Maybe I misunderstood but it sounds like you're suggesting steam and cast iron radiation behaves like forced air?

pecmsg

What’s given up during the off cycle was lost as it warmed during the beginning of the on cycle!

PMJ

@rorylane ,

You are on the right trail with this. The resistance around here to timer based control is mystifying. This market did not appreciate Ecosteam either which is a very fine control. At least @ChrisJ does. At the end of the day Ecosteam controls how long the boiler runs and when. The result is more even heat than anything pressure based can possibly do and at much lower, more efficient pressures.

You obviously have figured out that once your vaporstat is tripped your boiler doesn't need to run for a while.... and you also have figured out it would be best with a much longer wait than your vaporstat will ever give it. For the simplest solution I recommend a delay off/delay on timer where you can adjust both the burn time and the wait time and operate at pressures lower than the lowest vaporstat cut in would be in all conditions. With this method the amount the boiler is oversize makes no difference either and you just skip the vaporstat altogether.

But the timer you already have and what you are trying to do will be a good step forward. Post a complete wiring diagram of what you have so far. Some of us will help with this. We can do it PM if you wish and not ruffle any feathers.

Jamie Hall

I guess the thing I've never quite figured out, @PMJ , is how and on what basis do you vary the time delay on the off part of the cycle to account for varying loads on the system as a whole? Perhaps I've never had the misfortune to encounter a significantly oversized boiler...

pecmsg

> @Jamie Hall said:
> I guess the thing I've never quite figured out, @PMJ , is how and on what basis do you vary the time delay on the off part of the cycle to account for varying loads on the system as a whole? Perhaps I've never had the misfortune to encounter a significantly oversized boiler...
Best guestumate

The steam supply is absolute

The heat load varies

The timer is absolute

Sorry it doesn’t work!

PMJ

It is terribly simple and I have explained it multiple times but few wish to hear it.

You need to figure out how many minutes per hour your oversize boiler needs to run per hour to heat on design day. My boiler will heat my place at -20F running only 30 minutes per hour. At the simplest level all that is required is a fixed run/wait scheme that produces 30 minutes of run time per hour. I ran 10min on/10 min off at first. Slower cold starts but the more you need heat it will be really nice, even, and with no pressure. Maximum 10 minute runs is not enough to ever generate measurable pressure ever but 30 minutes per hour will heat on design day. Once a timer like this is installed with both run/wait times independently adjustable any size boiler can be handled with any number of cycles per hour you want.

This is the simplest level with about a $60 control. All that is required to have no pressure is to limit the max straight run time. All that is required to guarantee enough heat is a minimum run time per hour. You can do both with one timer setting in all conditions. This really isn't that complicated. It is not a theory. I did this for years eliminating my vaporstat with much improved results. I have gone way past that with vacuum now but even the simple setup beat my vaporstat walking away.

Do I really need to say that on mild days only a cycle or two satisfied the stat? Even then there is no pressure with this scheme.

rorylane

Thanks everybody for your comments here. I appreciate the insights to different approaches, it's all valuable information to me. I will post here with what I end up doing.

Jamie Hall

I'm right with you, @PMJ , on a seriously oversized boiler. It's a perfectly valid and simple approach. And I'm not deaf. Where I have trouble understanding the concept is its application to a system with a correctly sized boiler.