Triangle tube pte110-ng short cycling

tonyk

Had it installed in June knew it was over sized but the brochure says it ideal for small zones without short cycling. I have 1000 ft house slab needed extra space anyway now that's it getting cold, around 40ish at night there is ch call it gets to 120 target then cycles every minute or two still has ch demand, I have about 125ft of 3/4 inch copper baseboard. two things I would like to know, will this thing cycle less when it gets colder and is a buffer tank the only option I have to fix it which I don't want to do because i got this thing to free up space which is basically a closet.If I do have to get a buffer tank what size should I get

Thanks

Aaron_in_Maine

Buffer

Buffer tank could be an option. I would call triangle tube or have the installer come back and adjust parameters. Is the outside sensor hooked up to the boiler?

tonyk

short cycling

Yes, its hooked up target temp is 120 deg Wondering disabling it and keeping it at 180 would satisfies the thermostat quicker may bee less cycling

Aaron_in_Maine

no

No it would not.  You  need to adjust the differential the boiler is trying to stay within 10 degrees of the set point.  If you make it 20 to 30 degrees it will not solve your problem but it will help.

tonyk

short cycling

After all I have read I'm going to get a buffer tank installed would a 30 gallon be big enough?  Thanks

cattledog

Raising water temperature

With 125 ft of 3/4 inch fin tube you should be able to deliver enough BTU's to the space to match the minimum modulation of the TT 110 (approx 30K/btu/h). Check the charts from your bb manufacturer, but the slant fin charts I referenced are around 330 btu/ft. at 140F.



Running the system at 120F with a buffer tank and maximizing the condensing efficiency of the boiler may still be the best option, but you should determine what the cycle times are at higher water temperatures.

Zman

Cycles

I agree with the folks that think it should not be cycling. Given the boiler's turndown ratio and the amount of radiation, I would look elsewhere for the issue.

You have 125' of base all on one zone?

Check the boiler output percentage and the trimax. It should be increasing the on/off differential automatically to about 20 degrees.

Are all the radiators getting hot? I wonder if you have a flow/airlock issue on the secondary.

Carl

scott markle_2

Cycling

If your reset curve is set tight/steep, 120 could be a bit hot for this time of year, If your using a sensor boiler temp is of course a moving "target". Even with base it's possible to heat in mild weather with sub 100 temperatures. In my experience some boiler native controls make the mistake of trying to reach target quickly by ramping up quickly. This was a big issue on the early Viessmann boilers, the new generation have gotten much smarter as far as how fast they ramp up and how far past target they will allow the boiler to go.



One of the problems with buffers is that they don't necessary help this problem of ramping up too fast, intact some controls will "see" mass as load and it will cause the boiler to go to high fire even faster. I would start by getting your system to run in constant circulation by setting your thermostat to 90 and adjusting the reset to achieve your desired room temp. This probably won't solve the cycling but it will get your boiler temps down as low possible and boost your efficiency.



Another possibility is to set the maximum modulation on the boiler down lower, (I think you can do this with the TT boiler) I have done this with success on other systems and been really surprised by how low you can actually go. Also consider the parallel shift feature on the TT, (if it still exists on the new trimax) with this you can set a really tight reset curve and then wire a room thermostat to activate this shift if room temperatures go too high, this is the next best thing to a true indoor outdoor reset system like you would get with a Tekmar or a new Viessmann 200 system.



Buffers are great but for best performance you need a rig that's "smart enough" to hold a low modulation rate when loads are low.



I like to use a cheap 40 gall electric tank heater as a primary secondary "header"/buffer.

(nod to hot rod on this).electric elements tapings are not tapered but I'v had good luck with (German) locktight thread dope. Only limitation is system flow (3/4" tapings at the top), fine for modest residential apps. though.

Zman

TT

The triangle tube has a very smart controller. I have never seen one misread the load. It will patiently fire up and see what level it needs to modulate to in order to match the load. It will automatically increase the on/off differential at low fire.Unless the factory defaults have been compromised, no adjustments to the settings should be necessary, aside from outdoor reset.

What is going on with the supply and return temps on the boiler while this cycle is happening? What is the delta t and the on/off differential?

Carl

CapeCod

my two cents

I had a big thread going last year about the tt prestige short cycling so I always lurk here looking for others with that issue.  Sounds very similar to mine...in fact I am deliberately keeping the boiler off now even though it is getting chilly in the house because I know it is going to start short cycling with the low temps required combined with my low mass radiators.  I am awaiting a quote back to get a buffer tank installed so I can give some feedback after that.



The suggestion of the boiler ramping up too quickly seems valid to me.  I have spent countless minutes staring at the boiler last year and do remember seeing a huge flame in the beginning on the display and wishing it would start out small and slowing work it's way up to what is needed.  It seems to start balls to the wall and then back down once it starts reading the return temps and starts adjusting.  By that time, however, it is too late...it shuts down because it reaches temperature; only to fire up a short while later for another couple minutes.



I did call TT last year asking if the modulation can be capped at the upper end and still take advantage of the 5:1 turndown...no dice.

scott markle_2

Performance vs. efficiency

Conditions and connected system have so much influence here. Bad cycling seems to happen most on small systems at low load. Generally it takes a system a long time to get to equilibrium and we installers are out the door before we really see this behavior.



I can see how it would be really hard for a boiler control to interpret the real load, with just delta t. I'm sure the designers have to balance responsiveness with efficiency, in my opinion most systems (including Tekmar) are too performance oriented, they don't want to seem unresponsive so they ramp up much faster than they need to. From experience I can look at a house and "know" with relative certainty what my input needs to be at a give outdoor temperature. In other words when I go into a modest relatively tight house with decent radiation when it's 40 outside, I know with certainty that that boiler has no need to fire above its minimum modulation. But the boiler doesn't know how big or leaky the house is, it can't do a guesstimated heat loss calculation the way I can and its connected to a dumb on off thermostat, so the engineers had to figure a way that the control could look at rate of change in supply and return and interpret the load to come up with a target and differential. It works a amazingly well when the load is within the modulation range of the boiler but once you get bellow that point and the boiler needs to cycle it gets harder for the boiler to understand that it can stay in minimum modulation and satisfy the load.

tonyk

Short cycling

Let me add a couple things, the 125 foot is all one zone,I am including pipe with this measurement [not just the fin part]. I watched the display from a cold start,it started normal the modulated down[ it was condensing] when it reached target it stopped burning . I watched the two temps drop under 120 don't quite remember how low ,but kinda fast it fired again maybe 20-30 seconds then target reached again shut off maybe 90seconds then fired again the whole time there is a call for ch so its not heating the room to fast,but water is getting hot and cold to fast. I have the outdoor reset hooked up I don't see a deferential setting for ch in trimax control options It does seem to be getting better it went from 500 ignitions for 5 hours to 649 for 7 hours

tonyk

short cycling

Its just looked at the trimax manual notice the ch heating call blocking its set at factory 1 minute where should I set this 13 minutes ??

Zman

How much?

How much actual baseboard do you have?

Carl

tonyk

short cycling

After further inspection, I have 74feet of actual raidiation and 26 feet of that doesnt get much air circulation [wifes junk rooms]

scott markle_2

Not enough

That's probably not enough.



Base ratings are maximums, most of the time you don't need the rated capacity, and that's the beauty of full outdoor reset, you can actually run the heat all the time instead of being on an analog switch (on/off).



The only way you can solve this is with mass.

I suggest you do this:



Pull the elements from a 40gallon electric ,Insert 1" black nipples and unions, connect to boiler, (top taping to boiler return) Run base on a three way mixing valve with outdoor reset taped from the top of tank (return to bottom of tank) (taco makes nice simple valve/moter), indoor thermostat to zone relay to mix pump , TT to demand contact on mix valve. Calibrate the reset ratio (simple dial on taco) to match load, if you can't stand the fluctuations that wind and sun will make on a outdoor only controlled system (it's not bad) then you will need set the curve higher and use the thermostat,otherwise set the thermostat as a high limit and let the house warm up a bit on a nice sunny day, also forget about night time reset, when the sun goes down the house will naturally cool off, to hell with the programmed morning wake up, let the house warm up with the day (sun) , if its cloudy and windy it will be cooler so put on a sweater or burn some cord wood.



Oh yes you have to have a boiler demand make this a tank aquastat and run it on a reset curve with a wide differential, how big is your boiler?, bla bla bla sorry for this not very tight blabbering.

Zman

Higher temp

Adding a buffer tank will help your problem.

I know some folks will jump on me for saying this but...

You could try raising the boiler temp a bit and see if it helps. Many baseboard manufactures only estimate the baseboards performance at low temps. They don't actually test them.

The baseboard will transfer more heat at higher temps and this will reduce you cycles. Yes you will loose some efficiency (maybe not compared to short cycles), and you will not be matching you heat loss as closely.

I take the estimated part of the radiator chart with a grain of salt.

Carl

tonyk

short cycling

First of all thanks for all your help, I knew I wasn't going to get the most out of this thing when i got it. I got it to save space it basically sits in a closet, The thing that most worried me was the 100 ignitions a hour, I set ch call blocking to 13 minutes seemed to work good house was warm but circulatory basically ran all night, Do you think it would be better to set it to fan coil 140-180 deg to satisfy the thermostat quicker, right now I have it set for finned tube baseboard 120-180 deg

Thanks

cattledog

Yes, try 140F

If the circulation "basically ran all night", you are not reaching the thermostat setpoint and satisfying the call for heat with 120F water.



With the radiation you have, and given the system water volume and the boiler differential its possible you will get a 5 or 6 minute burner run at 140F before it shuts off due to over temp.



I did not realize that with the Trimax controller the CH blocking parameter worked after an over temp shut down as well as a satisfied call for heat.



Try running at higher temperatures and report back on system performance. The buffer tank supplying the system at 120F won't satisfy the thermostat either. With colder weather the output temperature will be up to 140F based on the reset curve. If you characterize your system at 140F where the baseboard output is more predictable you will be able to make a decision as to the cost benefits of adding a buffer tank and running at lower temperature during swing season.

tonyk

short cycling

Great math Cattle Dog, it took around 6 min to reach target 143 degrees. I'm wondering if I should change the CH call block time to 10 min from 13 min temp dropped about 25-30 degrees in that time lower to mid 40's outside 



Thanks

Stekay

Circulator Balance

I'm a homeowner, but pretty well studied here. I have a new (2wk old) TT 60. I made a significant improvement by increasing the firing curve to the 100deg - 170deg (cast iron rad) & slowed down the primary circ. (its a 3 spd) and the secondary is the Alpha automatic. The idea being to pull more heat out of the primary early. BTW i have 3 zones of slant fin. Hope that helps.

cattledog

satisfying the thermostat

Tony--



What does it take to satisfy the thermostat? It sounds like you are now running a 6 minute fire cycle, hit the high temp limit, the burner turns off, the pumps run for another 13 minutes, and then you fire again based on the CH lockout timer. How many of these cycles does it take to satisfy the thermostat. How long before the room cools down for another call for heat from the stat?



What has been missing all along from this discussion is a heat loss analysis. Do you have one?



In trying to understand and optimize your over sized boiler for the radiation you have, the first goal should be comfort. I don't know if your wife will care if you are condensing and achieving 10% more efficiency if you're not getting to set point.



Until you understand more about what you have, I would recommend you stop using the outdoor reset for awhile. Find out what it takes to satisfy the thermostat and understand the cycle times when you are doing that. If you are not satisfying the thermostat at 140 F, I would raise the outlet temperature to 160 F and characterize the operation. Dropping the lockout to 10 minutes is fine.



I understand that you are trying to run your new, over sized, high efficiency boiler in condensing mode, but given the baseboard you have, and the fact that you don't seem to be able to heat the space at 120 F output with near constant circulation you are near the edge. The situation at 140 F is not clear to me from the information you have provided. There will be a water temperature where you can achieve the room comfort. If that temperature is not providing for condensing, then you may want to add more radiation and a buffer tank.



For now, I would recommend that you get your system running in a predictable fashion with the room temperature reaching set point. I know you want to be condensing, and running longer burn times, but for now, in the words of a certain British philosopher "You can't always get what you want, but if you try sometimes, well you might find You get what you need."