Tekmar 256 or Honeywell Aquatrol AQ475A

Yingomat (System Engineer)

I planning to purchase a Outdoor reset controller, I have done research on the Tekmar 256 and Honeywell Aquatrol AQ475A. Both, have simmiliar features. I'd like to stay within the price range.
Which one would you recomend? problems? Any other manufacturers?

Your Help is greatly apprecieated.

ALH_4

reset

The Tekmar 256 is a good control. Do you have an indirect water heater or are you planning to install one in the future? If so, the Tekmar 260 would be a better fit. In my opinion, every boiler should have some sort of digital control.

-Andrew

Yingomat (System Engineer)

Thanks for the advise, I will consider the 260 for future upgrades

mark schofield

reset

A previous post about the AQ425 said it had a tendency to overshoot on boiler shutdown. I put one in last spring when I installed a new boiler and have noticed the same thing, at least so far at warmer OA temps. So I lowered the boiler max setting on the AQ so see the result. Possibly a characteristic of the WM WTGO3 I put in. The unit operates as advertised. It advertises to do the same as the 260; but the Tekmar has a digital readout menu so you can see temps, setpoints ect. The AQ425 has LEDs to show the status of the various functions. I put a temp guage in a well right next to the AQ supply sensor. I think for a few more $s I should have bought the 260 for the digital readouts.

mark schofield

differential ?

A thought on the overshooting. The AQ is supposed to automatically adjust the boiler differential. Possibly at lower temps with a lesser demand, the control keeps the boiler firing a bit longer so as not to have a really short runtime. Hopefully Bill@honeywell will give some advice.