Need set-up help for Tekmar 256

[Deleted User]

You said your load is 40,000 btuH and you have a baseboard output equivilant of 18,000 btuH. All the tekmar controls in the world aren't going to help that problem. You need about 2.22 times more baseboard if in fact your loss calcs are true...

Blue boxes can't fix every ill. Even if you do get the baseboard count up, you are still driving a tack with a sledge hammer. Not a very efficient use of energy, but boy howdy, does it get the job done QUICK :-)

ME

Roland_12

Need set-up help for Tekmar 256

Hi All,
I have installed a Tekmar 256 on my Burnham PVG-4 boiler. I set the boiler design to 180*F,outdoor min set to +15*F, the boiler minimum to 140*F, choice '4' for fin-tube convectors, and set the differential to 'AUTO'. Do I need to tweak this control in some way? how? Should I just leave it alone and let it do it's thing? I don't think the boiler is cycling differently since installing the 256. House temps are OK.
Does anyone know of a source of information for tailoring the Tekmars' settings to optimize it's operation? Thanks for all your past help, Roland

GLENN_14

The answer you seek depends on heating system design

You can play with max boiler temperature seting and design temp setting to get the control "dialed in". These two items will "shift" the heating curve and change the system temps over different outdoor temps. Is this your suystem or customer installed in another location?

Roland_12

256

Hi Glenn, Thanks for responding. It's my home system so I have plenty of time to experiment. The only negative so far is that it's taking much longer for the room temp to come up to thermostat setting on a really cold day.

Rich L.

ODR

Actually Roland thats part of what it's supposed to do, slow those temp swings and keep a more steady temperature. Is the slow response on every call for heat or just from a setback, such as overnight?

GLENN_14

is your home system baseboad or radiators or what?

Roland,
the other post is also correct in that you want longer run times at lower temps. This leads to more energy savings and better overall comfort. The trick in setting up the programming on the 256 is to determine the heating "curve" of your home. That will be determined by playing with the settings both design point (15 degrees) and the design temp for your system (180). You may have a typical situation in heat emmiters in which they are oversized so that you can get away with lowering the system design temperature. That will most effect energy savings. The longer system run times are fine. I run a modcon boiler in my own home which runs almost continually at a low output on design days. This design allows for great energy savings... Hope this works for you

Roland_11

256

The house has fin-tube convectors and the boiler (94KBTU output) is somewhat oversized for the amount of radiation. The Slant-Fin calculations give me a heat loss of about 40KBTU, which doesn't include any losses due to infiltration around windows or electrical outlets/switch plates. Still it's a bit bigger than it needs to be. I did seem to get better (faster) heating when the outdoor design was set to 25*F. Also, when the boiler is running, the 'Boiler Target' temp display (140-150*F)is always lower than the actual temp displayed (180*F) when the thermostat is satisfied. What would happen if I chose manual differential instead of auto? Thanks, Roland

GLENN_14

the oversizing of the boiler is normal

Sorry to say that the boiler being oversized is typical. Can you figure out the actual lenght of radiation in the home? The reason this is good to know is to determine the level of oversizing of the heat emitter. As for you changing the design parameters to 25 degrees, that makes sense that it effected the house as you raised the curve and had higher system temperature curves at each temperature. The problem is that you are lowering the efficiency of the system by raising the system design point. I would not recommend taking the control out of automatic mode as you can not best determine the spread that will most efficiently operate the system. The lower the temps the more efficient the system.

Roland_12

256

Hi Glenn, I have 36 total feet of fin-tube radiation. Roland...

GLENN_14

IF what you are telling me is accurate

The baseboard has way to low an output for the structure. standard baseboard is around 570 btu/lin ft and hi output around 770 per foot at design temps of 180. This translates to long system run times and a lot of wasted fuel. If your loss is actually 40k, I don't see how the system can possibly be working correctly. It sounds as though you need to ad radiation to the system in order to get the outpu up. Can you add more radiation to the system?? This would be a great help.

Roland_12

256

Thanks for your responses, I agonized over the Slant-Fin calculations and tried to find every worst case scenario and still came up with barely over 40KBTU heat loss. A real head scratcher for sure. As I have a mono-flo diverter 'T' system, it is not so simple to add radiation without throwing lots of scarce dough at it. The original boiler was oil-fired and cranked out the BTU'S at a prodigious rate. It kept the basement warm just from the radiation off the vent pipe. My actual measured stack temperature was over 700*F. I don't know the originl boilers' output as the plate disappeared long ago. Roland....

GLENN_14

Monoflow system also has some requirements

Roland,
The monoflow loop you describe may be attached to higher output baseboard than just the standard stuff. Also the pump required to "drive" the water through the system may be more that may have come with your new boiler. A good way to determine this is to measure the temperature difference between the supply water and the return water. If difference is greater than 20 degrees, you need to assess the pump to determine if it is actually a match for your specific system. So again more information is needed in order to help you.

Roland_12

256

Hi Glenn, The type of radiators in my house are semi-recessed cabinet types. I have only one 10foot section of conventional baseboard. The pumps (I have a 2 zone system, one for an indirect DHW tank) are Taco 007's. The measured (with an IR thermometer) delta T is nominally 20*F, 180*F on the supply and 160*F on the return measured at the boiler.
Thanks,Roland

Jed_2

Roland, download this!

http://www.beacon-morris.com/litlibrary/bmcv-7r.pdf

Measure your convectors and match to the btu outputs based on your 20 Delta T at 180 deg ave SWT.

See what you come up with

Jed

Roland_12

256

Thanks Jed, I did the calculations and came up with a radiation of 49600BTUs. Roland.........

GLENN_14

roland

Sorry for the delay in responding. I figured that you had some different kind of heat emmiters. They are actually convectors. you now understand that you have more heat emmiter than heat loss. You also explained that you have taco 007 pumps for the heat. in a monoflow system you can sometime see smallet temperature differencess due to the fact that the water is constantly "mixed" throughout the system. I am concerned that you do not actually have enough flow rate for the convectors as monoflow tees tend to increase pump head requirements. You might considera flate head circulator to increase the overall system flow rate such as a taco 0010. More money but a much better fit to monoflow systems. I can't help but wonder if the old system had an old series 100 b&g pump. Increasing the flow will inprove system efficiency as temps are overall higher and your system heat output will be better.

Roland_12

256

Hi Glenn, Thanks for taking the time to respond to my question. A Taco 0010 may increase the flow rate by as much as 50% based on the charts. It seems it would fit easily in the place of the 007. What would be the downside if it wasn't the solution to my situation? Lower delta T ? Would I find the weak spots in the piping (aka leaks) due to the higher flow rate? The original pump was a B&G. I don't know the model number, just the it was a silver/grey color. Thanks for your help,Roland