Teckmar 360 - settings for boiler protection

Arutneva

I just finished installing a new radiant system. I have an old boiler that needs protection from return temp below 140F. I installed a 4-way mixing valve (ESBE) and a teckmar 360 mixing control.



In the manual of the Teckmar 360 it says that if its the only control unit then the boiler sensor should be placed on the supply side of the boiler, However, my main concern is that I want to make sure that the return water is never below 140F so it makes no sense to install the sensor on the supply side. There is an option to install it on the return side, but the control of the boiler uses a "boiler enable" function, and it is only recommended if this one of multiple controls of the boiler.



To test the mixing valve and the teckmar 360 I tried the two settings:



1. I installed the boiler sensor on the return side. It successfully adjust the mixing valve so the return temperature is always above 140F. However, it leaves the boiler always on. Even when the mixing valve is completely closed it still calls for heat. The boiler has a temperature protection setting that shuts it off, but it leaves the boiler pump always on.



2. I tried installing it on the supply side, and in this case it correctly controls the temperature that goes to the radiators, and turns off the boiler when enough heat is in the system. However, it does NOT protect the boiler from, as the return temperature goes far below the 140F limit set in the teckmar 360.



Any ideas on how to setup the system so that it BOTH protects the boiler AND shuts it down after the heat demand is met?



The only way I can think how to make it work is to pair the teckmar 360 with the teckmar 256 (boiler control). The 360 deals with the mixing valve to protect the boiler from low return temperature and to meet the mixing temperature of the system. The 256 reads the 'on/off' enable from the 360, and reads the supply temp of the boiler. With these two variables it turns the boiler on and off.



But there has to be a simpler and less expensive way to do this.... Ideas? Thank you.

Zman

Tekmar

I would  put the sensor on the return side and use the existing boiler aquastat to prevent overheating.If you wire the boiler switch on the 360 is series (interrupting the circuit) with the boiler's aquastat, the boiler's aquastat will act as the max temp the boiler will fire. You want to set it fairly high so it will not interfere with the regular operation of the tekmar.

Carl

Arutneva

teckmar

Thank you Carl for the suggestion. My concern is that when the boiler (Burnham Series 2) aquastat shuts of the heat it does not turn off the boiler pump. The pump keeps on running because the main switch is still on. Therefore the boiler pump runs 24/7.



My two concerns are:

1. Increased electrical cost for running the pump 24/7

2. Premature failure of the pump.



My thoughts now are to either get a separate boiler controller (aprox $150) or re-wire the boiler pump so that it turns of when the safety aquastat switch is engaged. However, I do not know if this will have an adverse effect on the overall boiler functioning. Any thoughts?

Zman

Correction

I though you had an older controller. I don't think you can do as I originally suggested.

You have 7&8 on the tekmar wired to TT on the boiler?

It is normal for the boiler circulator to run any time there is a call for heat. It does this so that the residual heat in the boiler will be used before the next cycle begins.Even if the flame is out the circ should be running. Any time the tekmar displays the burner and flame on the screen it is normal for the boiler circ to be running.

It is also normal for the circulator to "post purge" and run for up to a few minutes after the call has been satisfied.

I think you are wired correctly. What is you boiler aquastat set to? It would be nice to set it a little higher than what the tekmar wants so the tekmar is always in control. Above 190 makes me nervous.

Carl

Arutneva

Tekmar setting on demand side

The 7&8 of the tekmar are wired to the T-T of the boiler.



Regarding the boiler circulator. Given that the tekmar is always asking for heat that boiler circulator is always on. The boiler does not cut power to it when the high temperature switch is activated. I have a second circulator, as shown in the image attached, that is connected to the teckmar (5&6). My plan was for this circulator to keep the water flowing through the boiler (and the house), without needed the boiler circulator to stay on.



The aquastat of the boiler is 180. The problem is that the tekmar never kills the power to the boiler. For example the tekmar calculate yesterday that the system needed 130F - for testing I set the boiler max to 220. It went all the way to the top until the safety cutoff of the boiler was triggered. I reset the max to 170F as it seems more prudent.



This only happens when the tekmar is configured to the temp sensor on the demand side. If I configure it to the supply side (and change the temp sensor) it correctly cancel the call for heat at a reasonable temperature just above what the system needs. BUT fails to protect the boiler from cold water......

Zman

Correct

If you have it piped just like that drawing, you want the boiler circ on. With the closely spaced tees, the other circ will not create flow through the boiler.

Carl