Condensing Boiler - Is this normal operation??

smithfan

I have a Triangle Tube solo 110 boiler with an outdoor reset. I take note of the target water temp and notice the burner will overshoot this temp by about 12 degrees or so. Then the burner kicks off and it the boiler will switch to circulator only until the water slowly drops back down to the target temp and the process starts over again.

This is all before the thermostat is satisfied. I guess I just assumed the "modulating" part meant the flame was suppose to maintain an exact water temp, but it seems it will overshoot temp by a bit and run the circulator until it drops down again.
Is this typical operation?

SWEI

smithfan said:

Is this typical operation?

For an oversized, underbuffered, or improperly commissioned boiler? Yes.

Aaron_in_Maine

Unless your house is 3000 sqft the boiler is over sized and if it is zoned it is even worse as far as run time of the boiler. The only way to know this is to do a proper heat loss. You could add a buffer tank to help with the cycling.

GW

Plus it's not even winter yet. Very minimal loads on the system these days. If the house is zoned then this is what one could expect. If it's not zoned it's still likely. Simple factors dictate how many btu the distribution system can unload.

smithfan

I have 3 zones, basement is infloor, which wasn't on at the time. And 2 upstairs, both fin-tube. The house is approximately 1400 square feet. Also, I've never had heat loss calculations done, but do agree the boiler is probably oversized. I understand this is common issue. So basically what your saying is the boiler is trying to work harder then it needs to? Are their any parameter adjustments I can make to the boiler programming itself to have it work more efficiently?

GW

Yes.

You're total heat loss is probably 30,000 to 40,000, if you're in new England.

Just let it be, add more house, or start all over.

smithfan

Yes i do. And, btw..I'm in Wisconsin

j a_2

I totally agree with the responses u are getting...it really sounds like ur boiler is oversized, big time...

smithfan

j a said:

I totally agree with the responses u are getting...it really sounds like ur boiler is oversized, big time...

Any recommendations? Trying to find out if there are any boiler settings I can tweak as a work around.

smithfan

180
110
-10
60

smithfan

CH Call Blocking Time = 03 x 10.2 sec

smithfan

Also, the only time I get a decent delta T is from the infloor slab heat, the upstairs zones I barely get in difference in supply/return temps.

smithfan

Fin Tube Radiators.

smithfan

Hatterasguy said:

You might make an experiment.

Reduce CH1 Maximum to 165°F. See if the house will hold temperature for the next 30 days.

Will do. So you think changing the curve will give it less wiggle room and allow for a longer CH burn?

smithfan

As far as I can tell the Solo 110 doesn't have a CH2 Circuit, so everything is on CH1. The Trimax does I noticed. My CH Call Blocking Time Factory setting says 03 x 10.2 Secs, where the Trimax Factory setting is 1 minute. Here is a Pic of my factory parameter settings for the 110 .

smithfan

I guess I'm not understanding what increments I adjust 3 x 10.2 secs. Where's the trimax are in Minutes, not seconds.

smithfan

Hatterasguy said:

smithfan said:

I guess I'm not understanding what increments I adjust 3 x 10.2 secs. Where's the trimax are in Minutes, not seconds.

Sorry, my bad. The Trimax has the better setup.

On that boiler, increase the value up to the maximum which will be "30 x 10.2 seconds".

Unfortunately, that's effectively worthless as it only prevents the boiler from firing for about five minutes (306 seconds). It probably doesn't fire for five minutes after it hits high limit even without that input.

The control for that boiler doesn't give much latitude to prevent short cycling as the supply water temperature drops.

If it gets onerous, all you can do is to give up efficiency and raise the heating curve to provide hotter water. The emitters will deliver more BTU's and satisfy the call faster. This was the traditional method of control 25 years ago when cast iron boilers had a permanent setting of 180°F.

TT has an expensive and complicated product there that doesn't function any better than 25 year old CI technology when installed in a house that is far too small for it.

The only real solution in your situation is to install a large buffer tank which adds mass to the system and requires the boiler to heat the tank and the radiation every time it gets a call.

That's what I thought..Thanks for the insight. Considering the boiler was installed 3 years ago (before I bought the house) it amazes me that proper heat loss calcs and boiler sizing are just not extremely common place now among installers. It's not like these issues are a secret.

I'll probably take your advice an turn the curve up, which is sad because I was so excited to be able to modulate based on outdoor conditions. Oh well:(

GW

What about a combi boiler?

smithfan

Okay, so I increased the CH Block function to it's max, about 5 mintues. So I'm getting about 5 minutes of burn time followed by 5 minutes no burn and circulator only time. This averages about 6 cycles per hour. Do you think I can live with this or is it too much wear and tear on the boiler? Still thinking about just taking hatterasguy's advice and bumping up the curve drastically.

smithfan

OH!! Yes, i got it.
And just curious, is there any need to make adjustments to the thermostat CPH settings?
Right now both upstairs honeywell programmable thermostats are set to 3 Cycles Per Hour.

smithfan

Hatterasguy said:

If the heating curve is dialed in properly and matches the heatloss of the house, the 'stat will call for more than one hour. Effectively, it is closed 90% of the time.

Even when you deviate from the ideal heating curve and raise the water temperatures, it would be nearly impossible for the 'stats to call 3X per hour. So, the setting is moot for your system.

Would you consider combining the two upstairs zones into a single zone and a single circulator? You will be able to control the temperature in the zone without the 'stat by throttling the flow with a valve in the basement. You adjust it over the course of several weeks until the two zones are perfectly matched. Then you leave it alone forever.

Yes, that's kind of where I was leaning. And actually since my basement is unfinished, it could even retrofit underfloor pex tube heating for entire upstairs, on 1 single zone. Then I could just get rid of all my base board.

smithfan

***Just an Update***
(those new to the thread, original problem was short cycling of an over sized mod-con boiler w/ 2 upstairs baseboard zones, 1 downstairs infloor slab)


So I tried an experiment today. 30 degress outside, and based on my curve my target temp is 150 degrees. I first ran all 3 zones (1 zone is my slab heat) at the same time to add more mass, which did in fact increase my burn time to 40 minutes!! I then ran both upstairs baseboard zones (without slab) at the same time and got a CH burn time of 25 Minutes.

So it would seem, running just 1 zone of the fintube baseboard at a time equals those short (cycle) burn times. So I'm considering programming my stats so both upstairs baseboard zones always run in unison, almost like having just 1 zone - to add more mass.

My ultimate goal is to also lower my reset curve so I can hopefully achieve lower target temps. Unfortunately lower CH temps are my only option for good condensation since a delta T
virtually non-existent w my baseboard zones and p/s piping. Although I do get an acceptable 15-20 degrees T when running all 3 zones at the same time.

My worry is the lower target temps with the new curve will lend itself to shorter cycle burn times again.

for fyi my current curve is dialed in at:

180
126
64
-10

smithfan

If I leave my curve in place, should I also scrap the idea of running multiple zones in unison more continuously and revert back to microzones with the setbacks and short cycling?

Is it a pick your poison type deal? Meaning I can have longer burn cycles but not necessarily low water temps or any savings.. or short burn cycles but more wear and tear on the boiler from running just 1 zone at a time.

smithfan

Although 15 minutes doesn't sound bad compared to 5!

smithfan

I agree. A buffer tank is the ultimate solution. And no, I cannot run each baseboard zone individually without short cycling. With my curve however, the individual stats do get satisfied in a relatively short amount of time. But as you know, it means I'm not using the lower water temps I'd like.
Do you think the savings in wear and tear, and future savings of fuel from running lower temps would justify the cost of adding buffer tank?
And..
On a side note, and out of curiosity. If you where to build a new house from scratch, what would your personal ideal setup be? I have a friend building a single story 3500' 4 bedroom home on a slab who is planning on using hydronic heat. I'd like to toss some ideas his way so he doesn't end up in the same boat.

Brewbeer

I agree with Hatterasguy, fuel savings alone won't justify the cost of a buffer tank. But if the buffer tank can reduce the cycles from 100 per day to 20 per day, the reduced wear and tear on the boiler probably mean fewer future repairs, and longer boiler life, might get you closer to the cost of the buffer. And you will have a boiler that should be more reliable in the short to medium term due to less wear and tear cycling.

smithfan

Is there any data the boiler will display that can tell me how many total cycles it did that day. Because that would be easier than sitting in the basement watching it.

Heat_n_CT

smithfan said:

Is there any data the boiler will display that can tell me how many total cycles it did that day. Because that would be easier than sitting in the basement watching it.

The first season she thought it was cute...now my wife just thinks I'm weird logging data 2-3x a day.

Brewbeer

smithfan said:

Is there any data the boiler will display that can tell me how many total cycles it did that day. Because that would be easier than sitting in the basement watching it.

Check the manual. This website: http://www.supplyhouse.com/Triangle-Tube-PT110-86000-BTU-Output-Prestige-Solo-110-Condensing-Gas-Boiler-w-TriMax-Control-NG

... states that the Trimax control features "... describes lockouts, stores solutions, stores last 8 errors and records sensor readings for 24 hours"

I have a Lochinvar, and it records number of space heat cycles, number of DHW cycles, and total run time in both modes.

smithfan

Thanks..I figured it out..The Prestige will tell you the total CH ignitions and total Burn hours. As long as I write it down along with the time I can calculate how my cycles per hour and hour many minutes on average per hour it ran.

I came up with another fancy idea. Considering I have a mixing valve for my infloor heat slab, I was thinking I could turn that way down, say from 120 to about 100 - and by running the downstairs heat more often, it will take much longer to heat the basement, at the same time it will introduce cooler water back into the boiler more often, which in theory will keep my overall cycles per hour down. In essence, it's like using my slab heat like a buffer tank - a large buffer tank..
Thoughts?

4Johnpipe

Slabs make great buffer tanks...lots of mass...in a manner of speaking.

Jason_13

I like my Alpines. Run different inducer speeds for CH and DHW, adjustable low fire hold times, change the PID on the fan from the display, adjustable diff above and below independently and now the Sage Zone control that you can program the zone size into the boiler and it limits the inducer to match the zone or minimum firing rate so sizing is still important.

smithfan

Well, with running the zones more in unison, instead of individually, in the last 24 hours I've averaged about 2.2 cycles per hour.

CMadatMe

In the end the biggest problems aren't the low end of the modulation rates but rather being forced by 99% of boiler mfgs to have to use fixed speed boiler pumps. It's the lack of being able to pull out all that flow rate of the boiler side when you don't need it that causes most of the short cycling issues. You're still moving the same gpm at low fire as you do as high fire. You can slow blower speed, do what every you want but that's still not solving the issue.

smithfan

So what are your brand options if you want a mod-con with a min fire rate of 10k or lower?

CMadatMe

Sorry sir but you're wrong on that aspect in my opinion. If a 80,000 btu/hr boiler has a pump on it that's moving 6.4gpm and you are only pulling 2 out to the secondary side where do you think that other 4 is going?

I'm a Viessmann guy smithfan. There's a reason why they size boiler pumps for a 40 rise.. Low boiler side flow rates. Not ideal but better then just about everyone else. It's also the reason why they want you to use common supply temp sensor (LLH Sensor). Boiler looks at system need, not it's own onboard temp sensor. I sat today and started up a B2HA150 (530,000) and watched it condense at 160 boiler supply temp. Lamda Pro does help with that aspect as well because you have control of the dew point.

The Vitodens 200 does have the capability to control a variable speed boiler pump as well as system pump but they're too scared to turn it on for the US. I think right now Lochinvar is the only one out there that allows you that function.

CMadatMe

Wrong..... Don't need a DT of 35 on the system/secondary side and the boiler if the system needs the muscle it will get to its output. Told ya, was condensing today with 160 boiler supply but my LLH temp leaving to the system was 142-145.. Most don't know nor want to take the time to learn the math, size/use the right pumps for the job and that's not the boilers fault.

CMadatMe

Hatterasguy said:

You state: "80,000 BTUH boiler". Since it's a mod-con, what's the lowest firing rate?

You state that you are "only pulling 2 out to the secondary side".

I presume you mean the secondary side is flowing at 2 GPM and the primary is flowing at 6.4 GPM.

If so, please provide the DT on the secondary side and I will calculate for you what the boiler does with the 6.4 gpm flow rate.

The flow rate will not cause the boiler to short cycle. Be assured of that (with the one caveat that the boiler's capability of measuring very minute DT's is limited).

As per your request. Sorry it's small, just converted it from my excel calculator I had made. You do notice the 14 degree difference between the system side return vs the actual boiler return. Boiler in this case is working on a 6 degree delta-t all because of that stupid fixed speed boiler pump. So in this case you still aren't even condensing. Pick the flavor of your choice. This was an ALP80 which is 16 on the low and pump is really 7.4 but only makes a difference of one degree or 135 on the boiler return.

smithfan

Just to jump in quickly, speaking of flow rates. I'm pretty sure the pump inside my boiler is a grundfos 3 speed circulator. The pumps on my secondary loop are all 3 speed circulators as well. If it is variable speed pump like I'm thinking, would there be any benefit of adjusting it up or down?.

CMadatMe

To stop any confusion here. When I refer to primary side, I'm talking boiler side, you define the system side as primary.

By operating my boiler pump at a reduced flow rate I can get into condensing faster and more often then with a pump with a larger flow rate. Most installers don't use Common Supply Temp sensors that are offered by just about all the mfgs. They rely on the boiler supply temp sensor. In the Viessmann world we always use a common supply temp sensor. The boiler wants to make sure that the system is seeing the supply water temp needed based on the heating curve. When you don't use it no matter piped with 2 closely spaced tee's or with a LLH you are going to get a temp drop once the system side flow rate exceeds the boiler side. When does that happen? When you need the water temp the most. On those 20 and below days/nights more then likely but a 2-3gpm reduction in boiler flow is a significant advantage to keep you condensing where normally you are not.

The only reason pump charts in manuals exist is for the high end of the modulation rate not the low end. As long as my flow doesn't drop below the low end I'm good. So in this Alpines case 1.6GPM. If you were able to vary the speed of the pump between 1.28 and 7.4 there would be no need to pipe primary/secondary as long as the system could handle the 25 degree delta-t or you piped a constant circulation system.

CMadatMe

My example was a boiler flow rate of 6.4 and a system of 2. Totally the opposite. Umm... Look at any boiler they all can't get the rated output unless the delta-t the pump is sized to can be met.. But because most mfgs don't trust contractors, they put one in the box they feel safe with.

Lastly, SYSTEM RETURN WATER TEMP when piped pri/sec can only influence BOILER RETURN WATER TEMP and water temp isn't the only thing that gets you into condensing mode. Guess you forgot about are little friend called CO2. In the Viessmann world I can control that, in the rest of the boiler world they can't.

I think what you seem to miss is that 95% of the time system return water is mixing with boiler supply water thus elevating the boiler return water temp. If the boiler return doesn't see that magic 130 from what everyone teaches the boiler doesn't condense and I don't believe that sales pitch. Why? Because I see it with my own eyes everyday.