low boiler temp or setback, efficiency

[tjs]

First I should say that I am not an HVAC professional.

My church recently replaced an old 1M Btu boiler for our hydronic heating system with 4 300 Btu boilers controlled by a Tekmar with an outdoor reset. We've had a pretty mild winter in Minnesota, and the Tekmar is typically setting the boiler temp at 140 to 150 degrees.

On a couple of the zones in the church, we have programmable thermostats, but I'm finding we can't really do a setback each night, because it takes the system 10 or 12 hours to go from 60 to 68 degrees.

What I'm wondering if if it is better to reset the parameters in the Tekmar so it is producing a higher boiler temp and then do setbacks at night, or just to leave the boiler temps low, and then keep the rooms around 68 all of the time. Or is there something better than either of these options.

One thing I've noticed is that the outdoor temp reading on the Tekmar is fine when it is in the 30s outside, but when it is in the teens or near zero, it is off by 10 degrees (the Tekmar thinks it is 10 degrees warmer out than it actually is). I'm not sure if this is because of where the sensor is placed (I actually don't know where it is), or if it is a calibration issue, etc.

Any suggestionswould be appreciated!

[heykiss]

As you found out the hard way, running reset with temp. setback has its drawbacks. Can you override the Tekmar control for a couple of hours in the morning and run the boilers at 185 deg. for short morning warmup?

[tjs]

Thanks for the suggestion. It looks like if we get a timer and set it up to indicate occupied/unoccupied, when we do a switch from unoccupied to occupied, we can get a heat boost for an amount of time we can specify. So I think we'll try that.

[heat/cool/dude]

First of all, your tekmar outdoor sensor needs to be mounted on north side of building. If you have baseboard heat I wouldnt set back any further than 2-4 degrees. I also would set tekmar to give you 180 to 185 degrees at an ambient of 0 degrees.

[onetime]

If your using the tekmar for setback and the t'stats also it will always have problems. I believe the tekmar has the capability for optimum start-up which brings the boiler temp up soon enough to warm the buiding up properly. With that don't set your t'stat setback more than 2F-4F. It should work ok. As far as the sensor being off its maybe changing the boiler water temp 5F or so, not a big problem. Water temp won't go below 140F anyway.

[ralphtheplumber]

the Tekmar is typically setting the boiler temp at 140 to 150 degrees.
Are the boilers running at ~180, and mixing the zones down to 140, or is that the actual boiler setpoint?

If it's the 2nd one, what kind of boilers are you running?