Running 2 CPH finally and loving it!

ChrisJ

I wanted to start a thread for this as it is brought up quite often.

After finally insulating all of my piping (except for fittings... I'm still slacking..) and adding even more main venting I decided to try 2 CPH on my VisionPro.  The first cycle stunk and I barely got steam to radiators and the second wasn't great but it kept improving.  After a day it became really nice.   My current set point is 70F and according to the digital thermometer on my 1st floor the temperature has been between 69.8F and 71.4F since Saturday (4 days).  My TRVs also love the extra cycle and are maintaining a better temperature.  I get steam quicker because everything stays hotter and the radiators heat less so that is less stress on the vents and maybe less water loss overall.



So far, I doubt I will ever go back to 1 CPH except for maybe in the spring and fall.  For all I know the VisionPro will compensate for that but something tells me it won't.

This is working so well I'm tempted to try 3 CPH but I've got a feeling it will be bad.

MDNLansing

Tell Me Please

Is the CPH the minimum number for cycles that will run in an hour? For example, run 2 short quick cycles per hour even if there is no call for heat.I am assuming it doesn't limit the maximum number of cycles per hour, but I don't understand this setting. I've searched the net and I have yet to find an explanation for this damn setting.

ChrisJ

Hard to say

I don't really get it either but this is what I think.

2 cycles per hour is what it expects to do when the system is at 50% load. Not sure what 50% is and I don't think it knows either. So I think its a starting point that is somewhere in the middle.



Meaning on warmer days it may only do a cycle every 2 or 3 hours. On a colder day it may only get 1 cycle in per hour but it will be a long one. I view it as its a way it plans how to react to temperature change. How soon it turns the burner on, how soon it shuts it off.



From what I've seen my boiler runs for shorter times, and more often set to 2 CPH. However it is maintaining a much closer temperature to the set point with little over shoot. Practically no overshoot in fact.



What I have noticed for sure is its not a fixed timing. After I changed the setting it did need to learn, but it did change its behavior based on how fast the room heated. It seemed like each cycle increased in time until it was happy and I guess its been changing the run times as ambient temps change.

ChrisJ

huh?

Preheat? What?



What are you using? Whatever it is I want one!

MDNLansing

He He He

Join the club and build one!

ChrisJ

build one

Building I can do, coding I cannot.

ChrisJ

Ah!

That is exactly what I wish my Visionpro would do. A simple thermal couple at the end of my long steam main is all it would need.

ChrisJ

Timing

I just kept track of its run time. Ambient is currently 23F.



10:28:50 start



10:30:15 : steam coming



10:32:00 : steam at radiators



10:42:35 : off







While a total run time of 13 minutes seems short it sure did heat the radiators plenty and it had no problems with the ambient in the high 30s so far.

ChrisJ

Steam coming

I've noticed just as the boiler starts producing steam I get a short pressure spike around 1oz or so. Immediately after this steam starts flowing up into the header.



Steam coming is that first pressure spike.



One main is 29' the other is 11'. My radiators all heat at pretty much the same time.

MDNLansing

Shorter Cycles

The shorter cycles (not short cycling) really aids in comfort. It allows the radiators to fill just enough to get hot to satisfy the t-stat. On mild days you might only need 2 of them, keeping the rads cooler. Colder days might get 6 cycles which pack the rads with steam. Overall, run time on the boiler is less with short cycles than with long drawn out cycles. Granted, some of the data I'm building is in my lab, but some is from my actual system. It's an old dinosaur, nut it's working for my experiments right now.



Surprisingly, I'm seeing the lowest gas consumption by running the cycle up to cut out pressure, letting it fade back to 0 psi, then the cycle over again until the t-stat is happy. Even with a 105 year old system there are things you can do to improve performance.

ChrisJ

More times

These include the first batch. It seemed like every other cycle is almost like a mistake because its much shorter, although it does heat the rads a significant amount. My only concern is the extra fuel used during the "preheat". Of course, I don't even know if there is extra fuel because the boiler and piping is staying that much hotter.





Without a doubt the house is far more comfortable and you don't even notice the heat.



10:28:50 : start



10:30:15 : steam coming



10:32:00 : steam at radiators



10:42:35 : off













11:32:35 : start



11:36:45 steam at radiators



11:41:35 : off













12:09:00AM : start



12:12:30 : steam at radiators



12:22:15 : off

PMJ

CPH

I settled in on 3 CPH during any call for heat no matter what. They are 20 min cycles and I vary the ratio of on to off time the longer it takes to satisfy the call. I also vary the first run time from call (preheat) depending on length of time since the last call. There is no cut in or cut out happening because I've never seen a pressure higher than 2oz anywhere.

ChrisJ

PMJ

What setup are you running PMJ?

PMJ

Setup

The programmable logic controller (PLC) I have posted about previously. Ladder logic programming - its a blank sheet of paper - you do whatever you want. Happy to answer any questions.

ChrisJ

Ah

I remember that now.

PMJ

Teco

Yes Mark, that is the one I am using. I really haven't used much of what it is capable of. My focus has always been simplicity and few moving parts. It does have a bunch of cool capabilities, analog I/O,PID and more for a great price. Glad to hear someone is giving this a whirl.

Ban

PLC

Mark, PMJ



Do you program these PLC's by any chance on the side? I'm sure a lot of us are reading this have already researched the Teco Sg2 and wished we knew someone who could do the programming(!).



RB

PMJ

Programming

Ban,



This stuff really isn't that tough. Software is free and use just plug in your laptop.

Programming examples in the free manual and you start real simple. You will want to do so much tweaking for your own system that outside programming would be a pain. The whole thing is $100-tops $200 and you practice in simulation mode on a table top not connected to anything. If you are interested just give it a try. We could help with questions.

ChrisJ

Solid state?

Why does he say he replaced them with solid state controllers? What isn't solid state about these? I'm guessing it uses mechanical relays, but why does it matter?

PMJ

Mechanical relays

I like the mechanical relays for this kind of work. They are much more forgiving for  wiring mistakes which might fail solid state outputs. You can hear them operate too which I find a helpful. I don't think cycle life is really an issue.

MDNLansing

Testing

Mind you, I am currently collecting data using my old boiler. I am tweaking various parts of the piping and testing different venting methods on the Eddy System to try and correlate air ans steam flow changes to system performance. I can't modulate the burner yet, but I am getting some good data.



I've got the controller running in a messy state. Simple code, wires going all over, sensors moving twice a day. I'm sure you;re familiar with what this all looks like. It's far from polished.



If I use the presurretrol, cut in is .5 psi, cut out is 2.3 psi. Thats as low as I can make it work. Using the sensors, cut in is 2 oz, cut out is 12 oz - 20 oz, depending on what I am testing. I can hold 20 oz for 6 mins before I have fallen to vacuum.



Temp swing right now are all over the place. With all the testing, its hard to establish an average. Without the modulation though, I am pretty sure I can keep it a constant 69.5 - 70.2 degrees though.



Currently, I have tweaked the system a little. I am no longer using the retarders on the main vents, only the radiators. Also, I have split the tapping in the main to vent to both the atmosphere and the air line. Once steam gets to the end of the mains, the vents close and the remaining air / steam is sent to the air line. This has allowed me to vent the mains very fast (empty to full of steam in less than 2 mins), and also send steam through the air lines to heat the vacuum vent and close that as well after a few mins.



I am learning a lot doing all of this with my controller. The Old Dead Guys were indeed great with physics and design. They built these systems to perform perfectly with always on low fire boilers. But with today's boilers they need some mods. Dropping a new boiler into and untouched original orifice system just isn't all that efficient. They need a little help. Based on what I have done so far, I should be able to fill all my rads with 200 degree steam from a cold start in less than 10 mins. Then, I should be able to hold the heat and fade off to 165 degree radiators over the course of 90 mins. Holding the vacuum for an hour and a half creates constantly changing pressure differentials between the rads and mains, and that keeps the steam moving through the system. Low temp boil for the spring and fall to get that perfect temp, and very long radiation in the deep of winter.

Mark N

Timing cycles

Chis have you timed anymore cycles? I have my thermostat set for 1cph and when I have timed the on and off times I find them to be very symmetrical. If it is in the 20's the boiler will run 20 to 22 minutes on and 60 to 65 minutes off.



Mark

ChrisJ

timing

Hi Mark,



No but I have noticed it seems like it runs longer now then it did earlier in the week. Unfortunately now isn't a good time to check anything as the wife hit the switch at the top of the basement stairs and shut the boiler off for a few hours by accident.



The good news is during a 6 degree recovery I only saw 6oz with 20F ambient. Went from 65F to 71F in around 40 minutes I believe.

Mark N

Tiiming

Thanks, it would be interesting to see what the pattern would be at 2 cph for the long term.

ChrisJ

Wondering

I have to be honest.

I'm wondering if in the long run the CPH setting does anything. Meaning, it seemed like it had been running longer and longer cycles. Then after my wife hit the switch by accident and I fired it up it of course ran for 40 minutes doing the recovery.



After that, it seems like its running really long cycles, slowly reducing them each time.



Makes me wonder if the CPH setting is nothing more than an initial recommendation and overtime the thermostat does whatever it wants as it learns.



Its a shame we can't simply get a real answer from Honeywell. Or can we?

ChrisJ

longer

Just timed it.



9:44:00 PM - start

9:45:50- steam is coming

9:48:00 steam at radiators.

10:04:35 - off



71F setpoint

23F ambient





See what I mean? 20 minute run time.

MDNLansing

Got it

I do believe I have cracked the code on the CPH Honeywell setting. It all has to do with tenths of degrees and number of cycles per hour. Here is how it works.



At 1 CPH the tstat will calculate at what temp the boiler should kick in and shut down with the objective of running the system only once in an hour. So, if you set the temp at 70, it might fire up the boiler at 69.5 and shut it down at 70.8. It's making the assumption that running to achieve a full degree swing will generate enough residual heat to hold the temp above 70 until the next CPH cycle starts, in this case one hour. The idea is that by modifying the start and end point allows the boiler to only run once per hour. Most of this seems mysterious because it is calculating all this using tenths of a degree, which most thermostats don't display.



Now, at higher a higher CHP, the start to end swing is lower. So, at 6 CPH we only have to hold the temp for 10 mins. So with a 70 degree set point, it might kick in at 69.8 and out at 70.2, knowing that in 10 mins it will run again. It doesn't overshoot very far because the next cycle is only a few mins away.



The undesired effects of CPH are mismatching the number of cycles per hour and the heating method. Your boiler may take 10 mins to fully fire, purge the air, and heat the rads. Once that's done, it might take another 10 mins to achieve the set point. At 1 CPH the tstat is going to account for this, plus overshoot however far it thinks it takes to ensure the room temp is over 70 degree for the remainder of the hour. In some houses this overshoot might be .4 degrees, in others it might be 1.3 degrees. It does incorporate building heat loss, but only what the tstat sense (on average temp falls .3 degrees every 15 mins).



In short, a CPH of 1 or 2 is recommended for steam. Setting it higher causes issues because of the initial warm up time. If you were to use a setting of 3, the boiler could short cycle on the second or third firing. Cycle 1 achieves the desired temp, then a few mins later the second CPH cycle starts and now the tstat thinks the swing only needs to be .2 degrees, causing the boiler to only run for a min or two.



The guy I talked to about this works for a Honeywell R&D facility just outside Detroit. He headed the project creating the digital thermostats (removing the mercury switch). The CPH concept was originally supposed to be a selling feature. They assumed lots of companies would move from mercury to digital and wanted a feature making their tstats the "most comfortable". He admitted to me though that the CPH doesn't work all that great, and they never used it to push their products. It works well enough to keep using in the tstats, but not well enough to claim it's better than the competition. He said that in order to make the feature truly useful and accurate, the tstat needs more on board memory and a processor to calculate averages over longer periods of time. Using off the shelf batteries in a small form factor just doesn't make this possible. They did develop some prototypes that had processors and more memory, but they were too big to be marketable. The Vision series units do in fact have the capability to improve the CPH function but at this time they aren't looking to develop it any further.

ChrisJ

Warmer weather

MDN,



What will mine do when its warm out, say 40s and 50s and the boiler hardly ever runs? It will cool down and need a good 10-15 minutes to run before steaming under those conditions.



Will 2 CPH still work?



Actually if I'm understsnding correctly, time really means nothing. It will simply shut the boiler off at a lower room temperature. So in theory, I should still get heat.



But why does it seem like it changes its run times? I've seen it when I first change from 1 to 2 CPH where it shuts off before I get any steam to radiators. There couldn't have been amp temperature increase and it was dark out so it wasn't from the sun.

Mark N

CPH setting

Enter 127201 into "search the wall". Read the threads.

MDNLansing

Load

The CPH calc is only used for predicting WHEN the system should run, not how long. The length for the burn is calculated using the load and duty cycle. So, a CPH of 2 means the tstat will attempt to stay as close to your set point as possible by running the boiler every 30 mins. In order to calculate the exact temp to stop the boiler, it uses a load calculation. So, at 2 CPH we know we need to run twice an hour, but now it needs to calculate what temp to shut down at. On warm days, that temp might be just a tenth of a degree over the set point. On cold days, it might be 1 whole degree over the set point. Units that have outdoor resets can predict this load quite easily, it's just simply the delta T over a given time period. But on lower end units with no reset, it has to record how fast the temp falls in your house and calculate this over and over. For example, once the set point is reached, on a very cold day, we might loose a tenth of a degree every 3 mins.So the upper limit is calculated by saying once we hit the set point, how much more do I need to add since the house is loosing 1 degree every 30 mins.



A reset model knows exactly what the outside temp is and can adjust this calculation quickly. So, when it's 10 degrees out, the house looses a tenth every 3 mins, when it's 50 degrees out the house losses a tenth every 27 mins. So if we are running a cycle every 30 mins, we only need to exceed the set point one tenth per cycle. And, on the cold day, we need to exceed the set point 1 entire degree (loosing a tenth every 3 mins equals one degree every 30 mins). The models without resets however can only calculate this by monitoring how fast the temp is falling over time at the tstat. So the tstat says, over the past 12 hours we have lost a tenth every 3 mins so we need to exceed the set point by 1 degree. This is far less accurate because it has to calculate this over and over and has no baseline. This especially is a problem overnight because you don;t have exterior doors opening and closing, stoves and ovens running and so on. The temp fall over night is very steady, but not very predictive to the conditions when people are coming and going and doing things in the house.



So all that being said, keep in mind this is a calculation. In the example you are talking about, the system probably calculated that it needed to run for 8 mins to increase the temp to the desired set point + calculated overshoot. However, that run time calc was based on data from recent boiler cycles when the boiler was already hot. So a hot boiler that just ran 10 mins ago might only need an 8 mins run to "warm up" the steam still in the system. Other times, the data might include instances where the boiler was cold and needed 25 mins of run time to increase .7 degrees, in which case it would probably overshoot by a lot.



This is why he was claiming to do this properly, you need to store lots of data over long periods of time and calculate run times by doing complex calculations. This is a classic challenge of bad data in, bad data out. Even the Vision series units can only record about 7 days worth of data. And, they can only do a simple calculation like "last time I needed a .4 degree increase I ran for 20 mins and overshot by 1 degree, this time I will only run for 8 mins to reduce the overshoot." This type of calculation is just too simplistic. You really need to do something like "when building temp fall off is .1 degree every 17 mins, and the boiler last ran 21 mins ago, and we are .7 degrees away from the set point, and we need the temp to exceed the set point for 30 mins, run time should be 21 mins." They just don;t have the brains to do this type of prediction.

ChrisJ

Outdoor

Which Honeywell models use an outdoor reset!?

I thought none of them had this ability?



I'd gladly upgrade from an 8000 series to something using an outdoor reset.

MDNLansing

None for Steam

As far as i know, the only Honeywell outdoor rest is for hot water heating. Its called the AquaStat

ChrisJ

heat loss

Is there a way to calculate my house's heatloss with this info?



Ambient : 23F. Dark and little wind if any. Setpoint : 70F. Boiler is an EG-45 and is 150K input and I think 94K out.



10:28:50 : start



10:30:15 : steam coming



10:32:00 : steam at radiators



10:42:35 : off













11:32:35 : start



11:36:45 steam at radiators



11:41:35 : off













12:09:00AM : start



12:12:30 : steam at radiators



12:22:15 : off

Mark N

Interesting

Chris it is very interesting looking a your 2 posts that show 3 heating cycles. They both follow the same pattern. Steam at rad to system off is 10 min, 5 min, 10 min. It would be interesting if that pattern holds for if you observed more heating cycles.

ChrisJ

pattern

Mark N,



I'm sorry if I confused anyone. I just copied and pasted the previous 3 cycles so people wouldn't have to go digging for the info.



I don't think the pattern held as it seems like run times increased but it may be my imagination. What I do know is this morning it was 5F ambient and my house was comfortable and the TRVs kept the bedrooms on the 2nd floor at their normal temperature. Its amazing to have a house stay around 70F and the bedrooms are held around 66F at all times from 5F to 50F ambient.

ChrisJ

Don't know

We had a fairly warm night last night and now a very warm day and I just noticed the VP shut down just as steam was getting to the radiators.  Zero heat was released into the t-stat room.



I guess it's confused because everything takes so long when its all ice cold from sitting all day.  Might have to use 1 CPH on more mild days?

ChrisJ

Nope

Nothing in the house changed. Oven is off and its dark out. No heat producing devices near the t-stat either.

Mark N

2CPH

Chris, about 3 or 4 years ago after reading a thread here I tried 2CPH on my FocusPro 5000. I was very dissatisfied with the results. I would get cycles like you just described. I went back 1CPH. When it is very cold outside the system remains hot enough in between calls for heat to work on 12 to 14 minutes runs. But when the boiler has sat off all day or for long periods it is not sufficient.



Also another time I set up a digital thermometer that reads in 1/10 degree increments right next to my thermostat to observe how it worked. This is what I observed over 3 cycles. My FocusPro was set to 1cph and set to 70 degrees.



When the reading on the digital thermometer read 70.5 the thermostat turned the boiler on. The boiler ran for approx. 20 minutes and shut off. The digital thermometer still read 70.5. Over the next half hour the reading went up on the digital thermometer to 71.5. When the reading fell again to 70.5 the boiler started again. It did the same thing for the next 2 cycles I observed.



Mark

Mark N

Recap

You tried 2cph and were liking it. Then you tried a Nest and didn't like it. Went back to VisionPro set for 2cph and had issues because of warm weather. What was the issue you had with the 1cph setting to begin with?

ChrisJ

Nest

The thing I dislike about the 1 CPH setting is the large temperature swings especially on cold nights. Right now during mild weather its fine but when its 5F out side the swing gets pretty big. Even with an ambient in the teens the swing can be annoying. When we see continuous cold weather this system set to 2 CPH is amazing. It's to the point where you don't know when the heat is on or off, it just maintains a very steady temperature.



However none of that is why i tried a Nest nor is it a big enough of an annoyance to really change much. I tried out the Nest to try and get data logging and the ability to check the system via internet. That is really a separate subject and the idea sparked after another member posted logging from his Nest. I'd love to be able to check up on the system when we are away. Sometimes we leave during the Christmas season to stay with my wife's parents in Canada so the house may be empty for a week or so at a time.



I asked about the Prestige series perhaps using weather forecasts via internet to predict run times. This is because I had hoped maybe those t-stats could work like my VP 8000 set to 2 CPH but know to run the boiler longer on warmer days and they also do offer data logging. I guess it's kind of a dream that will likely never happen. As I'm sure you already know there really is no problem running it set to 1 CPH, its just I'm always looking for improving things. I'm about to order more insulation to do my returns but that doesn't seem as nice as tinkering with thermostats.

Mark N

Just a switch

Chris a thermostat is just a switch. No matter how many bells and whistles they add that is still all it is. A boiler controller would perform the functions you are looking for. As previously stated they are expensive and overkill for residential applications. The CPH setting just replaces the anticipator used in the old thermostats. That setting determines how the systems operates. To set the cycle rate with the old style anticipator you needed to know the current draw of the gas valve and depending on what type of heating system the proper multiplier. That would determine how to set anticipator. From my own observation the higher you set the CPH setting the shorter the boiler runs. From what I've

read the cycle rate starts when the boiler shuts off. At a CPH of 1 the thermostat will wait 30 minutes to check if the point has been reached. If the set point was reached the cycle is over. If not the boiler will refire till set point is reached. Then turn off and the cycle is over.