will an I-Sense work on an Atag A325EC?

[sadanorakman]

Just bought an Atag A325ECX, and want a compatible opentherm thermostat.

Not very keen on Atag's Wize controller (usability or price)

Wondered if anyone has managed to get Remeha's I-Sense working on an Atag?

I tried to resist posting a new topic, but have googled extensively, and found nada! I understand some install an I-Sense on Intergas boilers with success.

All comments gratefully received.

 

[Dan Robinson]

Will ask in the closed section for you.

 

[ALEC1]

you should be fine...holland takes OT very seriously , to such an extent both viessman and vaillant have to produce converters from their proprietary bus system to Open therm

 

[sadanorakman]

Will ask in the closed section for you.

Thank you Dan; much appreciated.

 

[Dan Robinson]

you should be fine...holland takes OT very seriously , to such an extent both viessman and vaillant have to produce converters from their proprietary bus system to Open therm

So why doesn't Atag work with Honeywell Pack 5?

 

[ALEC1]

a honey well f*** up no doubt...

I really have no idea...I had a remeha work with a honeywell OT thermostat some way back..

what do Honeywell or Wayne say?

 

[Dan Robinson]

Not a lot as you might expect.... you know Honeywell attitude towards OT. Which is infuriating, but since my recent dealings I can kinda see their point to a certain extent.

Atag weren't interested as it wasn't their controller.

Honeywell weren't interested as it was OT and therefore not really trained up.


I have even tried to approach Honeywell NL in the past, but my Dutch obviously wasn't up to par

 

[sadanorakman]

you should be fine...holland takes OT very seriously , to such an extent both viessman and vaillant have to produce converters from their proprietary bus system to Open therm

Thanks Alec1... I have been hearing conflicting opinions:
My naïve thoughts were that the whole point of OT was to encourage cross-compatibility between boilers and controls, yet I hear the manufactures purposefully implement it in their own way, which can ruin any compatibility!

I was just hoping that with Atag being Dutch, it might stand a chance of working with the I-Sense. I did email Remeha, but they told me they did not know. ...I'd wager that they know full-well!

 

[Dan Robinson]

I'd wager it too.

What I would suggest is you gett he boiler fitted with hard wired controls is possible.

Then order the iSense just in time so that if it doesn't work a intended you can send it back under the distance selling regs.


Unless of course the iSense works as an on/off as well as OT rather than two separate models.


Alec and I disagree on this, but I have had no problems with the Honeywell CM series controllers working in conjunction with weather comp so you will get efficient flow temperatures as well as an easy to use controller.

 

[sadanorakman]

Good Idea on the distance selling regs Dan. I can use my existing on/off thermostat initially.

Re the Honeywell... I've just quickly googled, and cannot see that any of these are actually OT-based. Am I missing something?

 

[Dan Robinson]

The only OT Honeywell product supported here is the RF2 Pack 5


But I have not yet managed to get one to talk to an OT boiler.

You are right - it is meant to be an open protocol, but boiler manufacturers have locked it down to their own needs. Vaillant and Viessmann (I suspect) and performed a few cheeky tweaks and given it their own names.


Honeywell UK like to pretend that OT doesn't exist which is a crying shame IMHO.

The Atag can use on/off as well as OT, and it is just a case of switching the connector blocks that the two wires go into.

You can't however have both connector blocks populated.

If you are using a weather sensor with an on/off controller; then you will need to choose the correct curve for the heating.

It is all simple enough once you have read the manual.

 

[sadanorakman]

The only OT Honeywell product supported here is the RF2 Pack 5


But I have not yet managed to get one to talk to an OT boiler.

The Atag can use on/off as well as OT, and it is just a case of switching the connector blocks that the two wires go into.

You can't however have both connector blocks populated.

If you are using a weather sensor with an on/off controller; then you will need to choose the correct curve for the heating.

It is all simple enough once you have read the manual.

I don't have an issue with understanding a manual Dan ...Well, unless it's poorly written

Correct me if I'm wrong though please.... I get the idea that you are suggesting a boiler fitted with on/off stat combined with WC is somehow an equivalent substitute for an OT stat controlled boiler?

 

[Dan Robinson]

Alec aptly monikered it as a Hybrid system.

You have weather sensor on the boiler setting the flow temp; and something like a CM907 with optimization enabled.

You set he curve slightly higher than you would if you had a fully integrated system like the Vaillants.

Then the two sides of the control system work blissfully unaware of each other to achieve a similar end result. I have used it with customers as well as at home (although I have the full monty Honeywell Evohome system in my place).

You need to set the curve to slightly higher than otherwise as there isn't two way communication and you need a little extra oomph to give a positive heat input to get up form the set back temps.

My system was sized very closely, so the emitters are over sized meaning the slope on the boiler is set much more closely.

I installed mine completely from scratch and have a fairly modern build house.

 

[sadanorakman]

Hmm... I understand what you are saying, but it sounds somewhat of a fudge.

I understand how the WC will give a sort-of-appropriate supply temperature based upon the outside temperature, BUT...

I cannot see how it can do anything to even out the house's temperature swings like OT can... you'd still get potentially large overshoots either side of the thermostat's set-point.

Regardless of external temperature, I'd like the heat output of the boiler to slowly throttle back as the room temp approaches the desired set-point.

It's like trying to maintain 70mph in a car... do you achieve it by gently balancing the throttle with minor corrective inputs (Opentherm), or do you change between foot flat down on the throttle, to foot completely lifted (On/off) every time you overshoot or undershoot your desired speed... It's not hard to figure which approach will give the smoothest response with the most efficient use of fuel!

 

[Dan Robinson]

I cannot see how it can do anything to even out the house's temperature swings like OT can... you'd still get potentially large overshoots either side of the thermostat's set-point.

You don't overshoot though.

The Optimisation takes care of that as does the proper design of the rest of the system.

A fudge it might be... but Fudge tastes nice.

If you can get an all encompassing controller then great - it is the best way.

If you can't, or you don't get on with the way such a controller works, then my suggestion is the best of both worlds.

Tried and tested. Not only with customers but in my own houses.