Tekmar 260 settings


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Old 10-06-10, 07:15 AM
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Tekmar 260 settings

Hi Guys,
I installed a tekmar 260 without an indoor sensor, with the following settings:
Room occ 68
Room unocc 64
Outdoor dsgn 0
Terminal unit 4
Boil indr 70
Boil dsgn 180
Boil max 170
Boil min 120 (There is a boiler bypass)
Fire delay 10 sec
Boil diff AD (auto differential)
The boiler sensor is installed right at the output of of the boiler.

When there is a call for heat the tekmar target is 140 degrees and it will keep the burner from firing until the water temp is 110. It takes less than 2 minutes for the water temp to reach 140. The boiler is short cycling (it is over sized).

Would moving the boiler sensor after the bypass help? The boiler will run at higher temp which will make it run longer.
Also when the boiler is getting tuned I'm going to ask the technician to reduce the nozzle by one or two sizes.

Thank you.
 
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Old 10-06-10, 06:34 PM
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You want the supply sensor on the pipe that feeds the distribution system. For example, on the header right before you split into zones. So yes, outside the bypass.

If you reduce nozzle size, make sure you still stay within the boiler spec for allowable nozzle size. Going outside of spec can lead to problems.
 
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Old 10-06-10, 07:10 PM
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Thank you xiphias,
I already moved the sensor and noticed an improvement. The current nozzle is 1.75x45b, the next size down is 1.65x45b, the next size down is 1.5x45b.
Would the pump pressure be the same if i went with only one size down? Do i have to increase the pressure? or does it need to be detriment while performing the tune up?

If going with the second size down, Is the boiler going to work properly by increasing the pressure?

I checked the boiler's manual and searched online trying to find the minimum water temp recommendation by the manufacturer with no luck. It is a burnham V88 (cold start). Is the boiler bypass going to provide sufficient protection if i set the minimum temp to less than 120?
 
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Old 10-06-10, 07:51 PM
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I don't know squat about nozzles, pressures, and such. Hopefully others will chime in on that.

In theory, for oil boilers the return temps that start causing condensation in the boiler are around 113-115F. So 120 is about as low as you want to go.

But the bypass should help. You should monitor return temps over this heating season and see what they are for a given outdoor temp, number of zones calling, runtime, etc. Might be you stay at 120 or above, or if well above then you could potentially dial it down a bit. Just remember that replacing a corroded boiler will cost a heck of a lot more than you'll save with 5F cooler water....

And you need to make sure you're getting the comfort you desire with your reset settings.
 
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Old 10-07-10, 07:14 PM
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I'm going to leave the minimum set to 120, for now I'm thinking of combining the smaller zones by having the pumps of 2 zones run using one thermostat to avoid any re-plumbing and reduce short cycling.

The plan was to re-plumb the heat system and have a variable mixed injection but the budget did not permit. Hopefully next summer this will become real. The 260 will control the boiler and DHW and a 356 or a 361 will control the mixed injection.
 
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Old 10-14-10, 12:57 AM
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Doesn't condensation happen at 140 for all carbon-based fuel combustion in boilers?
 
  #7  
Old 10-14-10, 04:01 AM
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No. Gas is around 125-140. Oil is around 110-125. There's a 2004 paper from Brookhaven by Butcher that describes the various combinations of fuel type, excess air, humidity, etc. and resulting condensation temperatures.

http://www.bnl.gov/isd/documents/28709.pdf

For the simple case, see figure 1. The text is also illuminating.

Butcher says you want the return temps at least 10F below the given condensation temperature in order to benefit from condensing. This is a point made well by Carol Fey in a cool article or two. Basically, that minimal condensing temperatures may promote condensing in the flue and produce condensate, but that does not necessarily mean you are condensing in the heat exchanger where you can reap the actual efficiency gain.

To Condense Or Not To Condense
Carol Fey - Column - Plumbing and Mechanical


Discover the Magic of Condensing Boilers
 
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Old 10-14-10, 08:24 AM
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Originally Posted by esalman View Post
Hi Guys,
I installed a tekmar 260 without an indoor sensor, with the following settings:
Room occ 68
Room unocc 64
Outdoor dsgn 0
Terminal unit 4
Boil indr 70
Boil dsgn 180
Boil max 170
Boil min 120 (There is a boiler bypass)
Fire delay 10 sec
Boil diff AD (auto differential)
The boiler sensor is installed right at the output of of the boiler.

When there is a call for heat the tekmar target is 140 degrees and it will keep the burner from firing until the water temp is 110. It takes less than 2 minutes for the water temp to reach 140. The boiler is short cycling (it is over sized).

Would moving the boiler sensor after the bypass help? The boiler will run at higher temp which will make it run longer.
Also when the boiler is getting tuned I'm going to ask the technician to reduce the nozzle by one or two sizes.

Thank you.
boil MAX needs to be higher than boil design.
Take the differential off auto and make it fairly large, that will allow the boiler to stay firing longer, and stay off longer. Yes you end up with hotter water temp than you want, but it averages out with the cooler water when the boiler is off. The advantage is you reduce the short cycling, this will save more than higher water temp.
Having said that, in the auto setting, the control may learn the system and stretch out the differential itself.
 
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Old 10-14-10, 01:56 PM
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Originally Posted by TOHeating View Post
Having said that, in the auto setting, the control may learn the system and stretch out the differential itself.
Which it seems to do better in some systems than others. (And my limited experience and knowledge of PID logic suggests that it is better on systems that have a relatively constant demand such as 1-2 zone systems where if 2 zones the more they both run, the better. Multiple/micro-zoned systems with irregular demands are probably harder for PID to settle.) Key is to give it at least a couple weeks (4+) to learn on auto before messing with it.

My own system with 260 is two zones, one of which is 98% constant from Nov-Mar, the other is 85-90% constant due to internal gains from cooking, occupancy, solar. Depending on demand, outdoor temp, indoor temp, etc., the autodiff will range anywhere from 18-24 degrees and the cycling is very predictable and reliable. It would probably be less so with a fixed diff. But all systems are different. Try it and see.
 
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Old 10-19-10, 12:29 PM
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TOheating, Would setting boil max to 185 and setting the fixed differential to 60 be sufficient? to start with.
 
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Old 10-19-10, 06:04 PM
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I just increased the boil max to 180, reduced the boil design to 170, kept the boil min to 120 and left the auto diff.

Currently I'm using the wood boiler, with an aquqstat strapped to the return of the wood boiler, the aquastat is set to 160 with the differential set to 30. The oil burner will not turn on unless the return water temp is below 145 giving that the tekmar 260 is not keeping the burner from firing.

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Old 10-20-10, 03:46 PM
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60 degrees is a wee bit large.
That would be 30 degrees on either side of the target.
I would start at 10, and see how the cycles time out
 
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Old 10-20-10, 04:41 PM
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The maximum diff setting allowed by the tekmar is 42, so after thinking about it, this morning I changed the settings to the following:
differential 40
boil max 180...the boiler's aquastat is set to 180 so the water temp will not reach 200
boil design 170
boil min 130....so the water temp will not go below 110

Do you think the differential setting is still too large?

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  #14  
Old 10-20-10, 06:23 PM
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yep.
The idea is to reduce short cycles, not run the boiler and store energy in it.
You want it to still be weather responsive.
 
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Old 10-20-10, 07:05 PM
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What would you recommend for a differential setting?

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Old 10-21-10, 04:28 AM
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Originally Posted by TOHeating View Post
60 degrees is a wee bit large.
That would be 30 degrees on either side of the target.
I would start at 10, and see how the cycles time out
Like I said,

I would start at 10 and see how the cycles time out.
 
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Old 10-22-10, 09:26 AM
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I had to set the differential to 30, the boiler runs for 4 minutes before it reaches the limit, the small zone is causing short cycling when set to 10 and 20, the boiler would run for a about 2 minutes before it reaches the high limit. I have to combine the remaining small zone with another zone. I did combine another small zone with a larger zone before. I used one relay control both circulators instead of replumbing the zones. it seems like I'm going to end up with 4 zones instead of 6.

Currently I'm monitoring the temp of the different zones in order to locate an indoor sensor in a spot where the tekmar 260 will get the average temp feedback. Eventully I want to end up with system simillar to xiphias' system and have constant circuilation. The heat load is going to be consestant and then I'll enable the auto differential and let the tekmar do its magic.

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Old 10-22-10, 11:20 AM
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Try just running the small zone with out a boiler call.
It's not all the straight forward, but if the zone has a lower BTU per sqft loading then it will call less than most other zone and may satisfy just from stored energy in the system,
Do you have an indirect ?
 
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Old 10-22-10, 11:51 AM
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I'll try.
No indirect DHW yet. Next summer I'm going to re-plumb to have provissions for indirect DHW and replace the 6 circulators with one cricuilator and zone valves.

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Old 10-24-10, 09:14 PM
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If you get a tank in tank indirect (triangletube) than you can run that small load off the outer shell and draw off the energy in the tank.
I do it all the time with small inflow loads such as bathrooms, very very well.
It will work with other types of tanks but the triangletube does not seem to cycle as bad as a coil style indirect.
 
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Old 10-25-10, 05:28 AM
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Thank you for the advise. I tried to run the zone without the boiler running. The zone was not satisfied. This zone is tricky (kitchen/breakfast area). The area is almost 600sf, 3 outside walls. There is not enough baseboards, about 35 linear feet. I'm thinking to have the garage zone (pump) come on when the kitchen zone calls for heat. The garage has an air handler, I wounder if this will work.

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  #22  
Old 10-26-10, 05:36 PM
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put a buffer tank in.
You could go out on a limb and try the Tekmar Tn2 or Tn4.
The zone load coordination should stage the zone well enough to come on with other zones most of the time.
More costly than a buffer tank IMHO, but a better way to go.
 
  #23  
Old 10-26-10, 07:43 PM
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What do you think of a tekmar 369 zone manager? it is discontinued but I found few places selling it.
 
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Old 10-28-10, 03:10 PM
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NO, NO ,NO... RUN AWAY
That requires special (discontinued) thermostats.
Will not work with out them.

Buy the Tn2 stuff, I think it's priced pretty good, and has more features than that old relic.
 
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Old 10-28-10, 05:29 PM
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Thank you TO. TN2 it is, I have a a dumb question about the buffer tank....
Do i need boiler protection (boiler bypass) with the buffer tank? Or is the tank itself considered P/S protection? The tank will be great not just because it is going to prevent short cycling the oil boiler, it will help store more of the heat from wood boiler and probably reduce the use of the oil boiler.

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Old 10-28-10, 08:01 PM
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U still need boiler protection, even more so actually. If the tank is cold, it will stay that way longer.
It will store energy with the wood boiler, and you may want to make it bigger to store the extra energy from the wood boiler.
 
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Old 10-30-10, 04:41 PM
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Thank you TO.

 
 

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