Burnham K2 Operation

tennybrink

Long-time reader, first-time poster, and was wondering if anyone might be able to offer some insight on the operation of my Burnham K2 Boiler (100k btu). I had a friend who installs boilers professionally (on a much more commercial scale) help me install the unit, but he wasn't necessarily familiar with the K2 itself in terms of tweaking the settings to optimize the boiler efficiency.

I decided that I'd try to do the research to determine the optimal operating parameters for the boiler (my first one), and I'm finding the product literature comes up way short.

To provide a little context, this is for an in-slab radiant heat application (5" concrete, with 2" of XPS below the slab). I'm heating a "barn", but it's a fully finished barn with 2x6 walls filled with open cell foam, and 12" of cellulose blown in the ceiling. The barn is located in Michigan, and so far this Winter has been quite mild. The barn has 2 zones, one 6-loop zone heating approximately 1,400 sq. ft, and another 3-loop zone heating 700 sq. ft. Total system piping is less than 30-feet (right next to the boiler) The loops are made up of 1/2" pex spaced about 12" apart, with consistent loop lengths around 225'. I also have installed the outdoor air reset. I've only been heating the barn to 50 degrees through the last month, and have burned through 180 gallons of propane. That seemed a little high given the mild temps, so I've decided to look into optimizing if possible.

A few of the questions I have are below.......

1. I have the Sage 2.1 controller on the boiler, and it indicates supply temperature and "rate" (the manual doesn't speak directly to what the "rate" represents). Which leaves me with the question, what "rate" should I be striving to achieve? If the rate is an indicator of modulation, I suspect that a rate of 100% would indicate that the boiler is fully modulating and this would be a good thing (this is where it typically is indicating). If the "rate" represents the operating rate (fuel consumption level) and I'm always fully at 100%, I suspect that's not something I'm striving for.

2. As for the supply temperature indicated, it's usually in the range of 95-105 degrees, this seems low, but perhaps low is good as it requires less fuel. If in fact the "rate" illustrates modulation, and I'm getting 100% modulation at a low temperature, I suspect that's a positive thing?

3. The system has an Uponor manifold with valve controls to control the GPM flow through the loops. I have them all wide open at 1 GPM (as high as they go), but that's only because the documentation for the boiler specifies a minimum flow of 5 GPM, and I figured that correlated (6 loops at 1 GPM equals 6 GPM returned to the bolier?). I question my assumption here, because the 3 loop configuration would never achieve 5 GPM flow under this thinking. I noticed that if I reduce the flow in the manifold, my boiler supply temp increases (rate also begins to drop at a certain point depending on how far I reduce it, but I'm unsure of my rate of fuel being used is dropping, or if I'm losing modulation efficiency).

4. Last question, pump speed. I have Grundfos circulating pumps on each loop with 3 speed settings. I currently have both pumps set to high. What impact might adjusting the pump speed play into the equation?

I apologize for the lengthy post, but would be most appreciative of any insights that might be provided!

Thank you for your time.

Jason_13

One important question is what is the heat loss of the building.
Sound like very well insulated. Why 100k? I would guess heat loss about 30K.
How old is the slab? When was heat turned on?
Maybe locking into low would be better.
What is the operating hours and boiler cycles under the status screen?

tennybrink

Thanks for the response Jason.

The heat loss for the building was around 60k, after factoring in all the windows, and 3 sets of large sliding doors. Also, the ceiling is vaulted all the way through so it peaks at 22' in the middle, a lot of cubic space. I went with the 100k versus the 80k figuring with a 5:1 turn down it wasn't an overly aggressive upgrade.

The slab is about 8 months old, and I just turned on the heat around the 15th of December (lucky for me it was in the 40-50's still).

As for cycles, it's run for about 180 hours during the last 35 days. The cycles are up around 850, but 10% of those may be attributed to me experimenting with figuring it out.

I thought about locking into "low" tonight as you suggested, rather than "auto". What would be the negative ramifications of this, if any?

Thanks again Jason.

Robert O'Brien

3. The system has an Uponor manifold with valve controls to control the GPM flow through the loops. I have them all wide open at 1 GPM (as high as they go), but that's only because the documentation for the boiler specifies a minimum flow of 5 GPM, and I figured that correlated (6 loops at 1 GPM equals 6 GPM returned to the bolier?). I question my assumption here, because the 3 loop configuration would never achieve 5 GPM flow under this thinking. I noticed that if I reduce the flow in the manifold, my boiler supply temp increases (rate also begins to drop at a certain point depending on how far I reduce it, but I'm unsure of my rate of fuel being used is dropping, or if I'm losing modulation efficiency).

Flow through boiler is not dependent on system flow rate, or at it least it isn't if piped correctly.

CMadatMe

Boiler is over sized, it's the low end of the modulation rate that's biting you. Min modulation rate is 21,000 Btu/hr which is pretty much 80-90% of the load you need at design temp which we spend about 2% if the year in.

More then likely not pulling out the fixed speed flow rate of the boiler pump into the system so it's causing elevated boiler return temps. Also, most don't use the Common Supply Sensor that's available so the boiler is looking at system temp not the boilers supply/return temp sensors. I'd add the sensors and since you're zone pumps this:

https://file.ac/5CdWisGaB8A/Sage Zone Control Value Sheet.pdf

tennybrink

Thank you again for all of the feedback, it's been very helpful. I started putting this barn project together about 2 years ago, and unfortunately during that time my original hvac guy passed away unexpectedly. He'd already purchased the majority of the "pieces and parts" for the install design, and being a small independent contractor (and a great guy) I made sure to take care of all of the associated invoices for the planned install. I ended up with lots of "pieces and parts", but was missing the most critical part, the knowledge!

Many of your suggestions got me thinking about a few things.....

As for the system design, the temps weren't designed to be only 50 degrees, that's been my own "non-technical" attempt to try to conserve propane. I believe 65 degrees was the design temp used. It seems counterintuitive, but would the boiler perhaps run more efficiently if I bumped up the temp on the thermostats?

Also, there is a loft of approximately 500 sq. ft. above the workshop (the 700 sq. ft. section), which I had planned to add a 3rd zone to if I found it necessary (I figured heat rises, so I might not need it). The actual sizes of the 2 zones being heated currently are 1,501 and 711. I've attached pictures to add some context.

As for the suggestion of the sage zone controller, I looked at the product literature and noticed it seemed to indicate that it required the sage 2.2 software, but I'm only on the sage 2.1 controller. Truth be told, the main 1,501 sq ft zone is really the only one that runs 90% of the time. Usually the heat from that zone satisfies the other. Do you still think there is applicability to upgrade to this zone controller?

I'll have to look into the "common supply sensor" a little more to see if that might be applicable (by look into, I mean determine what it is ). I do have a sensor on the supply and return water temps that the boiler illustrates on the control panel. The system is a closed loop system (water only, no anti-freeze). Let me know if that impacts your thoughts on this at all.

I'll attach a few pics of the boiler panel as well. It's not pretty, I've been too focused on function alone to get things cleaned up .

Thanks again!

tennybrink

Barn pics attached to add context to layout. Thanks again!

Rich_49

You need another heat load calc performed . Give me the 4 wall dimensions and what doors and windows are in each , what type doors and windows also , include the long wall heights , how many inches of foam in the walls and ceiling . Don't forget the loft . It is not very involved , I will perform the calc , give me your town for weather data .

You're probably gonna need a buffer tank of some sort

CMadatMe

Rich said:

You need another heat load calc performed . Give me the 4 wall dimensions and what doors and windows are in each , what type doors and windows also , include the long wall heights , how many inches of foam in the walls and ceiling . Don't forget the loft . It is not very involved , I will perform the calc , give me your town for weather data .

You're probably gonna need a buffer tank of some sort

Now that's a great offer that shouldn't be passed on!!! I'm guessing 25K radiantly... Def going to need a buffer tank and would install the common supply temp sensor.

tennybrink

I agree! Thank you both for your guidance, you've gotten me a lot further along in the last 24 hours than I feel like I got in the past week trying to play phone tag with support troubleshooting things.

Thanks for offering to perform a heat calc Rich, I really appreciate it.

Dimensions are as follows:

West Wall - 68' x 12' (less windows - 46 sq ft)

East Wall - 68' x 12' (less windows - 42 sq ft , 1 fiberglass door (half glass) 21 sq ft, 2 sliding barn doors 40 sq ft EACH)

South Wall - 34' x 12' (to 20' at interior peak), Total wall area is 534 (less windows - 24 sq ft, 2 sliding barn doors 60 sq ft EACH)

North Wall - Same as South Wall (534), (less windows - 35 sq ft, 2 sliding barn doors 40 sq ft EACH, 1 set of in-swing french doors fiberglass with half glass (upper loft to deck) 42 sq ft.

East and West Upper Loft Walls (interior, but exposed to cold attic), 6x22' each side.

All construction is 2x6, with open cell foam in the the walls, but only to about 4" (R-13 to R-15).

Square footage of ceiling area is 2,300 sq ft exposed to the attic. Blown in 10" of cellulose, R-38 Value.

All Windows are Low-E, U-Factor of .30

All 6 Sliding Barn doors were made by me, I did sandwich 3/4" of XPS on the interior of the doors (plus 3/4" of wood on each side),, probably an R-Value of 4 or 5.

Foundation has 2" of XPS underneath the slab, and 2" of XPS extended down 48" around the perimeter. The slab is 5" thick, and the pex tubing is stapled to the foam (at the bottom of the slab).

Floor Space of each zone
Zone 1 - BBall area - 1,564 sq ft.
Zone 2 - Workshop area - 748 sq ft.
Zone 3 - Loft (not yet installed) 484 sq ft.

Town is Belmont, MI (49306), Grand Rapids is the closest metro area.

Hopefully this provides enough detail, Thanks again Rich, I really appreciate it!

Rich_49

Tenny ,

Please provide room by room measurements . Sorry for the confusion . BBall area , exposed wall lengths and what windows and doors in them , Same with Workshop area and loft .

Is the roof insulated throughout and are the kneewalls insulated in the loft . Separate the rooms for me and I will do the heat loss and give you everything you need . What spacing was the tubing put in at . Middle of slab would have been best but we can work with it

tennybrink

No Worries Rich, details are below.....

BBall area (46'x34')
West Wall - 46'x12' (less 32 sq ft of windows)
East Wall - 68' x 12' (less windows - 29 sq ft , 1 fiberglass door (half glass) 21 sq ft, 2 sliding barn doors 40 sq ft EACH)
South Wall - 34' x 12' (to 20' at interior peak), Total wall area is 534 (less windows - 24 sq ft, 2 sliding barn doors 60 sq ft EACH)
North Wall - Non-Exterior
Ceiling Sq. Ft. 1,750

Workshop Area (22'x34')
West Wall - 22'x12' (less 14 sq ft of windows)
East Wall - 22'x12' (less 14 sq ft of windows)
South Wall - Non-Exterior
North Wall - 34'x12' (less windows - 27 sq ft, 2 sliding barn doors 40 sq ft EACH)

Loft Area (22'x22')
East & West Walls - Each is 6' high by 22' long, knee walls insulated with R-13 to R-15 open cell foam.
South Wall - N/A
North Wall - 22'x8'
Ceiling Sq. Ft. 550

Ceiling is insulated throughout to R-38

Tubing was installed with approximately 12" spacing throughout the slab.

Hope that helps, Thanks again!

Rich_49

These reports are for 100% water . The Delta for parts are widened to 15* to keep head loss reasonable . 55* B Ball area , 60* Workshop and 70* in the Loft . Please tell me where the manifolds are ( how far from boiler) and what size pipe was used to get there . If you tell us the rate per gallon of Propane we can estimate fuel usage . You can gain alot by guaranteeing the Delta by using different circs , worth the investment . Designed this at -7* .

Gotta ask why you only ran 6 loops for the B Ball area ? It should have had 9 . Please show us a picture of the boiler and near boiler piping , also the manifolds . Don't leave anything out .

tennybrink

Thanks so much Rich! I'll snap some pics in the AM, and provide some more details.

A couple items to note, I upped the bball area temp to 62 degrees this morning on the thermostat, and when I got home this evening the room was up to temp. I checked the firing history, and it didn't fire at all between 4:30-10:45 (25 degrees out the entire time). I was out there until about 11:20, and it fired twice during that 35 minute period, but at a very low rate (30%) for about two minutes, then it would start to climb for a minute, and reduce back down and shut off. I'll check in the AM and see if this cycling continued.

From a temp standpoint, the outdoor reset has the setpoint at 130 degrees, but the supply temp rarely breaks 105 (I've never seen it hit the setpoint). The return temp usually runs about 15-20 degrees below this temp. When the fire rate is very low (30%), the supply temp is usually around 80, with the return 7-10 degrees below that.

Thanks again!

tennybrink

Rich-

I've posted all of the attachments below.

The system is 100% water, the only difference is the design temps were 65 degrees in all zones (I've been keeping it low to try to conserve fuel, but that may have been causing more short cycling it's sounding like).

I went and checked the boiler at 7:30 am this morning, and the 2-hour fire rate showed that it hadn't fired at all in the past 2 hours. From 4:30 pm yesterday until 7:30 am this morning, the run time logged 4 hours, and showed 12 cycles. I've kept the temp at 62 in the BBall area, (The workshop area stays around 58 just as a by product of the rooms not being separated). Perhaps setting both to 62 would increase the load a bit and reduce the cycling a small amount?

The reason I went with 6 loops was really based on the fact that I unfortunately didn't have a lot of knowledge in this space. I used some Loop CAD Design software, and put in my parameters (I had calc'd around 60k btu heat loss), and it spit out the loop design attached below. Probably not the wisest choice . I figured my personal calc was probably wrong on the heat loss, but the boiler had already been purchased, and I figured the fact that the boiler could modulate down to 21k btu's, but up to 100k, provided me a little margin of error (again, not my best assumption).

As for the loop Piping, you'll see it's not much in terms of overall length. The Primary section of the loop is piped with 1" copper, while it's reduced to 3/4" on the secondary (the "why" behind the 3/4" is because I essentially inherited all the "pieces and parts" and they were all 3/4' fittings). I did install a ball valve at the "tee" just in case, but right now it's remained open.

The pumps are Grundfos 3-speed pumps. I have both pumps (the 3rd zone for the loft isn't yet installed, I was going to play it by ear based on the need with the heat rising up there) set to "High" currently. Would reducing this to medium or low have a positive impact at all?

The Manifolds are Uponor, and I have attached a picture. I currently have all loop valves wide open. Any adjustments to these that might be beneficial?

All other adjustments that can be made to the current configuration seem to be at the boiler level (change modulation from auto to "low", or possibly reduce the max rpm settings for the fan).

Hopefully that's a comprehensive enough update, Thanks again Rich!