wiring diagram for new tekmar 256 based on my old reset controller

robyns

I have honeywell T475 A1032 1:1 ratio reset controller and I am thinking about replacing with Tekmar 256 unit. but need help with wiring.

Here is some info

boiler rudd senimaster copper tube

24V AC transformer

Robershaw gas vlave 2 wires with standing pilot

Watts flow switch FS10

High limit control

Honewell Reset T475A1032 which I would like to replace with tekmar 256

2 groundfus pumps, non of tthem are connected with exsitibg wirirng and I am going to keep them as is.



Here is the exsiting wiring file

Tim McElwain

You could

go to www.tekmarcontriols.com and get a wiring setup.



I would wire it as follows:



Input (Boiler Sensor) to terminal 1 boil



Input (Outdoor sensor) to terminal 2 out



24 VAC to 8 & 9 terminals hot to R common to C



Between 7 & 8 is your relay in the 256 control. Wire as follow take "R" + and wire to one leg (hot leg) of the transformer. Wire the other side of the transformer to 9 C-.



Wire one leg of the thermostat to "T" pin 7 and the other leg to 9 C-  



Then 5 and 6 will be wired as output to the boiler control as follows



Jumper from "R" to 6



5 to the boiler high limit from the limit to flow switch to the gas valve and then from the gas valve to "C" pin 9



That should do it.

robyns

connetion between "T" and "R+" on tekmar diagram

I don't have any thremostate conneted to control the boiler. so connection between T7 ( Input boiler demand signal) whta do have to do?



This boiler supposed to trun on and off based on water tempareture which will be compansated with outdoor reset controller.



do have to connect T 7 to C9 jumper?

Tim McElwain

I don't think it can be done without

a thermostat otherwise the gas valve would be powered all the time. There has to be something to shut down boiler circuit until a call for heat.



Try getting some help from Tekmar maybe they have a way around it.

robyns

what about connection between # 6 to #7

Hi,

what if i connect # 6 to # 7 T, so that when tekmar 256 ask for heat based on outside reset, switch between 5 and 6 will close and complete circuit

Tim McElwain

If Iam not mistaken the relay coil between

7 & 8 has to be powered to close the relay switch between 5 & 6. The Boiler Sensor and the Outdoor Sensor then control the heating curve.



If you go on-line to the Tekmar web site they have a complete manual on the 256. Look for Tekmar - Data Brochure Boiler Control 256.

robyns

from tekmar website

Boiler Demand T7 and C9

To generate a boiler demand, terminal T(7) must be connected to terminal C-(9)

through a switching device.



Boiler Contact - 5 nad 6

The Boiler terminals (5 and 6) are an isolated output in the 256. There is no power

available on these terminals from the control. These terminals are to be used as a

switch to either make or break the boiler circuit. When the 256 requires the boiler to

fi re, it closes the contact between terminals 5 and 6.



above info I found on Tekmar website.

which means I can connect T7 to 6 and connect gas valve, flow switch and high limit all in series at 5 and other wire end at C9. so when 256 ask for heat it will close switch between 5 and 6. which will complete circuit. so the Boiler demant is like outdoor reset is asking for heat and when it get high limit, 256 will disconnet 5 and 6 switch.

once I install my unit I wiil update here.



Thanks







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