Possible Tekmar replacement or tweaks?

fixxxer0

First post, but been reading here for over 10 years for help tweaking/fixing my one pipe steam system and programming the Tekmar.

I have a 2 story building with 4 apartments in it. I occupy one, directly over the boiler room (hottest one), and have issues with overheating in general due to poor balancing but that will be something I have to address later.

I currently have a Tekmar 279 with an outdoor reset, condensate return temp probe (located on the furthest riser in the cellar, not the wet return) and 1 apartment sensor in the coldest apartment farthest from the boiler. I have cycle length set on AUTO but there is one significant limitation in the Tekmar which is making me want to replace it.

If the set apartment with the ROOM temp sensor at or even above the SET temp (say 70* set with a 72* reading in the room) the Tekmar STILL fires the boiler a minimum of once per hour, which means it hits the steam established then turns off because the cycle length is basically 0 minutes. This causes overheating especially on warmer days. I called Tekmar, and they said there is no way around this, short of wiring some type of seperate thermostat cutoff into the power line from the tekmar to the boiler, which will have separate drawbacks/issues.

I am considering replacing the Tekmar now, because my now hidden in a finished ceiling temp probe for the steam temp is giving me OPN errors, and sometimes not showing the temp. causing even more issues.

What is the next best option for a 1 pipe steam boiler thermostat? Not sure if other equipment could use some of my existing controls/temp probes, but i'd like to go wireless as much as possible because running wires in this building is a nightmare.

I’d like to have the ability to have some wifi control, but also don't want to run into short cycling issues.

Long Beach Ed

I don't have an exact answer for you but I've used the Tekmar 279 for years. Do you use more than one sensor and average them? Have you set the Warm Weather Shut Down? I know that's not exactly what you want, but it certainly helps. Did you ask if the 289 control which replaces this one does the same thing?

In the end, I found that using a simple Honeywell thermostat and averaging four or six indoor sensors did a better job of regulating the heat. But that may just be my experience with my buildings.

Hopefully someone will have a better suggestion for you. You can look at Heat-Timer, but I've found them to have NO customer support, and we installed many of their products.

EBEBRATT-Ed

Tek mar is the best. The other option is a Heat Timer which is big $$$ and does not work as well. Balance the system with venting and run the pressure as low as possible.

LRCCBJ

I've also used the 279 for about seven years. Because of the unknown algorithm regarding the room sensors (which Tekmar refuses to divulge), I decided NOT to use them. I tweaked the heating curve, and the radiator venting over the course of one year and got it to the point where MOST apartments (there are six on three floors) maintain a comfortable temp throughout the year. A couple get up to 74° or so on occasion…………..not a concern for me. I run it on a 45 minute cycle which keeps the insulated mains quite warm and gets steam to the end of the mains in less than two minutes.

As mentioned, the WWSD is your best friend. This one is set to 62° due to plenty of residual heat in the building from people and cooking.

If you are dead set on keeping the sensors, you could use the second sensor in a different room and the 279 will average the two. I understand the difficulty in wiring it…………..!

The probe for the steam temp is notorious for failing. I've already gone through three of them. You need the capability to access it.

ratio

Tekmar seems to use a standard 10K type 2 sensor. Any sensor that's 10k type 2 (or 'CP') will work. I'd try one of these: https://www.workaci.com/product/425?v=5322 for the steam line. (There's a possibility that the steam line doesn't use that sensor, please verify.) And, you can average a square number of sensors (4 [2x2], 9 [3x3], etc.) with no issues (aside from keeping the wiring straight!).

Long Beach Ed

The Tekmar sensors are NTC thermistor, 10 kΩ @ 77°F (25°C ±0.2°C) ß=3892