Tekmar 260 question

Hi

I am installing a new Bias B4 cold start boiler in my home, along with a Tekmar 260 boiler controller. One thing on the Tekmar has me puzzled: the Unoccupied Building mode. The only way I can see this can work is by having the optional indoor sensor installed; But, the Tekmar manuals make no mention of the indoor sensor being required for proper operation of the UnOcc building mode? Anyone help me here? Also, I assume the supply temperature is NOT monitored, and that the high limit Stat sets the boiler temp. when the boiler is heating water for the DHW indirect tank (DHW priority mode)?

Pete

 

I moved your question to the boiler forum where hopefully Furd or Xiphias will see it. Both of them know more about this control than I.

 

Nope, not this kid. The only Tekmar control I ever had any experience with was a four-way valve with a proportioning motor. I never could get that silly thing to work and the plastic coupling between the valve and the motor kept breaking. I finally locked the valve in one position, completely re-designed the supervisory control system (two boilers working in a lead/lag operation with outside reset of the circulating water temperature) and called it good.

My experiences over the years is that generally speaking the more sophisticated a control system is the longer the payback time by means of fuel saved. I'm talking DECADES to recover the initial investment but increases in fuel costs will tend towards a quicker payback period, maybe ten to twenty years.

I once zoned a residence to have the bathroom only come on in order to have a warm bathroom when the single family member who arose at 5AM went in. After a few months of testing it turned out that it took about 45 minutes of burner time (or about 40 cents worth of fuel) versus running an electric space heater in the bathroom for 5 minutes at a cost of 3.5 cents. In that particular situation the zoning and control system would NEVER pay for itself.

It is my opinion that in the vast majority of residences the simple things like first having the proper sized heating system, sealing the building envelope, properly installed double (or triple) paned windows, high R-value doors, having optimal (and properly installed) insulation along with heat-recovery air exchangers will do more for saving fuel dollars than will high-tech boiler controls. Once these primary things are taken care of a person can then look at the boiler controls.

 

Many thanks Furd. Knowing you had worked in commercial applications I figured you were "experienced" in some of these wing ding controls. My feelings are pretty much the same in that the cost of these controls more than eats up the energy savings but never having used any I had to actual data to back up my gut feeling. Not only are the expensive up front but the more things there are to break, the more things will break & the more sophisticated the system, the more it will cost to fix when it does break.

 

Not sure. I'd have to read through the literature again. I don't own one, yet, but am thinking about it. For the DHW, I think it fires to BOIL MAX or the aquastat limit (if aquastat limit is lower than BOIL MAX).

The supply temp is always monitored (and reset) for a space heating call. I think the above logic applies to the DHW regardless.

As for unocc, it may be expecting a tekmar thermostat or 031 timer that talks to the control, or a remote sensor as you suggest. It MAY be smart enough to just turn down the supply temp.

If you can't find it in the literature, call tekmar tech support. Those guys are very helpful.

Also completely concur with furd about the first things being envelope (heat loss) and boiler sizing. There is no better investment than insulation, efficient windows, reducing infiltration, etc. We did a modest remodel last year and cut the heat loss in one room about in half just with good windows, can light upgrade to airtight, and better insulation in the ceiling/attic over.

 

We redid all of the windows six years ago, and had new doors installed last year, as well as having the attic insulation increased to the max. reccomended by our contractor. I don't how much more I spend before I end never seeing the savings vs. the costs.

The Tekmar was purchased at a factory special price, well under what they are advertised for. It was originally going to be used on a high-mass multifuel fuel boiler that would have benefited from a setback controller more than the Biasi will. But, it will do the indirect DHW control so thats a plus. As far as I can see, their stats only call for heat and don't convey any other information to the controller. The 031/032 timers only provide a closure or open depending on the time settings. I was planning on using the FAN position on the stat for the main zone to pull a relay contact to provide the unoccupied building mode. It does look they the shift the supply water temp in the unoccupied mode, but how they can regulate the building temperature is what I don't understand.

Pete

 

Sounds like you know it better than me. But check out the indoor sensors 076/077. Perhaps that's what you need for the occ/unocc to provide feedback to the control.

Failing that, try tech supt.

 

Went back and reread the manuals several times. The supply temp is monitored on DHW during the purge cycle ( up to four minutes.) Apparently the unoccupied room mode is determined by the controller based on outside temperature and supply temp.