service call ????????

Mike T., Swampeast MO

"The Buderus powers up the transformers alternatly depending on if the control is calling for open or close."

I believe this would avoid the problem entirely:

1) Connect a SINGLE transformer to CONSTANT power whenever the boiler system is energized.

2) Use ONE of the 110v outputs of the boiler to actuate the coil in a DPDT 110V coil relay with the normally-closed position of your relay feeding whichever Tekmar contact way you find most appropriate in the unlikely event of relay failure. Which boiler lead to use will again depend on what you want to happen in the event of failure!

3) "Neutral" problem when using transformers--even worse with multiple transformers--can be unbelievably frustrating. I would connect the BOTH transformer leads (hot and neutral) through the DPDT common relay contacts and "jump" the NO/NC connections to board neutral--maybe even two separate wires. (It's not supposed to make any difference if you just connected the neutral from the transformer directly to the Tekmar but...)

Steve Ebels

Buderus/Tekmar interface

Here's one I don't understand.

Situation is an eleven year old Buderus gas boiler with their 3220 control running a Tekmar mix valve. The Buderus control sends 110V power to either of two Honeywell transformers. One is for open one is for closed. The transformer output is 26V, as it should be. These transformers do their thing OK when not connected to the Tekmar but this problem appears when they are hooked up to the motor. When one powers up (open for example) the other terminal powers up also. However when you take the supposedly unpowered wire off the Tekmar the motor will operate properly. Also, the unpowered wire shows no voltage on it when the other transformer is powered. Like I said though, when both are connected to the motor and either is powered up the supposedly unpowered terminal show voltage on it also. This causes the motor to chatter loudly and remain in a fixed position.

What could be causing this??

Terry

why 2

why 2 transformers???

problem could be that the "common" for one is not "common" for the other.

Use 1 Transformer & a 2 pole relay to send power to proper side (and 1 common!)

Perhaps a diagram of what you have would clarify.

Regards,

Terry

Dale

The sec. of the second trans.

I think something may have happened in the motor where the secondary of the other transformer is now a load to the motor see if there's any voltage to the unused tfmr comimg from the wires on the motor.

Paul_6

does this valve head

operate by cam and micro switch? because it sounds to me like you have a switch that has failed in the wrong
position, or has gone out of sync. my two cents worth. I would add that if you have two xfrmr that either you have two motor windings, or someone twinned them together origanally to increase the va. Paul

Steve Ebels

2 transformers

This is the way the boiler and control have been operating since installation in 1991. The Buderus powers up the transformers alternatly depending on if the control is calling for open or close. I should clarify that the Tekmar actuator is a new replacement. The old on still worked motor-wise but has stripped a gear and will not turn the valve. (Compounding the situation is the fact that this recently widowed lady has a whole house full of Entran-II) But that's another problem.

Can't draw on this thing so I'll explain the wiring in more detail.

There are 2 110V outputs on the boiler control. Each one feeding the corresponding transformer. The R terminal from each transformer feeds the corresponding terminal on the Tekmar. One Transformer is for open and the other is for close. The C terminals are wired together in series and feed the common on the Tekmar.

Here's an example of what happens. With both Xfmrs connected to the Tekmar, an application of 24V to either the open or close terminal results in a reading of 35V on the supposedly "dead" terminal. When I take the unpowered wire off the Tekmar, there is no voltage showing on either the xfmr wire or the terminal on the Tekmar and it operates correctly. The same thing happens when the alternate wire is connected or disconnected.

I don't now how to determine if I'm getting some wierd backfeed situation or if the new Tekmar is internally messed up. Also why does the old actuator motor work correctly and the new one doesn't?


PS: Why do these things always happen on service calls that are 60 miles from home??

Paul_6

Im going to go out on a limb

and say that the old motor was mechanically switched, and the new one is electronicly switched, and you are getting feed back through it's circuit. I can't help you much because I'm not familiar with this particular valve motor, but it sounds to me that since it "hums and chatters" that you have both windings energized at the same time and it won't drive in either diriction

Steve Ebels

Paul

That's exactly what's happening but I don't know why. The person at Tekmar said he thought (but wasn't sure) that I had a defective actuator. I'd really like to know for sure B4 I order another one and find out that it does the same thing. Especially on a 60 mile (one way) trip.

Mike T., Swampeast MO

MUCH of this problem would be eliminated

IF the US (like much of the rest of the world) had used 220v (two wire--both alternately hot/neutral) like Tesla wanted. Not only would there be smaller/fewer wires but such systems are MUCH easier to utilize efficiently! (Wonder why 110v A/C units are such energy wasters?)

hot_rod

Could it be

It the old motor was stripped I'll bet the 4 way is seized or tightened up to the point the motor cannot turn it. A very, very common problem in older non barrier tube systems.

Does the motor do this when not attached to the valve?

hot rod

Steve Ebels

Hot Rod

> It the old motor was stripped I'll bet the 4 way

> is seized or tightened up to the point the motor

> cannot turn it. A very, very common problem in

> older non barrier tube systems.

>

> Does the motor

> do this when not attached to the valve?

>

> hot

> rod

Steve Ebels

Hot Rod

The valve itself turns easily and when one or the other wire is disconnected, the motor will drive it all the way over without problem.