Originally posted by HenGus
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Atag IS24 Plus Evohome Plus Opentherm
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The only way to know I've made the right choice would be to run 2 boilers side by side.
As far as I'm concerned I have an Atag iS32 with 10y warranty (life time exchanger) which is built to last near enough 20y. It seems to work well with evohome, though I'm still to use it in anger in the cold.
Only downside is I felt 24 was too small and 32 too big, but they don't do a 28. Ultimately I'm planning to extend my house and the extra hot water heating capacity is certainly useful so 32 it was.
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Originally posted by blowlamp View PostDidn't HenGus buy his Atag in an effort to work around a perception (at the time) that Evohome/OpenTherm wasn't compatible with Intergas boilers? On that basis, I think he probably found the best boiler for his needs.
I don't blame them for their choice, but don't try to say ATAG is a better engineered product than Intergas because it isn't (especially when you put cost into the equation).
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Is good news if solved once and for all. As I've said before price difference for me was aprox £500 more for the Atag (compared to slightly smaller eco RF). Admittedly that was comparing two different installers and maybe two slightly different installs.
Main thing for me is the installer seems to have done a cracking job and the pros I've shown the pictures to have been very impressed with the pipework etc.
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Update. Two weeks in to the present heating season, I confess that I am increasingly impressed with the ATag IS boiler and Opentherm control. At the moment, my 12 zones (19 rads) are running with 3 at 20C, 4 at 18C and the rest at 15C. The boiler is almost silent in operation with a flow temperature of 50C and a return temperature of 39C.
I appreciate that it is by no means cold at the moment but the other things that I note are the stability of the zone temperatures and the lack of HR92 activity. I have my boiler set at CH 65C which I may drop by a few degrees if the mild spell continues. A new boiler with Opentherm is still something of a learning experience.
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@fergie. Looking at the boiler info last night and again this morning, I am pretty sure that Opentherm overrides the manually set CH maximum temperature but not the TMax temperature set in the profile. My installer left the boiler on this profile setting: CH Tmax: 70°C; Gradient: 5; Heating line 19
This morning when I came down to make the obligatory cup of tea my boiler, with 4 zones heating, was showing an A3 setting (T-set temperature (calculated) in °C) of 70C: 5C above what I had set manually on the CH max temperature control. Now with all the zones within the target temperature range, A3 has fallen to 55C and A0 (flow temperature) is 41C and A1 (return flow temperature) is 39C.
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My boiler is in the garage so not that easy to sit and watch all the time. It’s a pity there doesn’t seem to be an easy way to produce output logs.
Anadotaly my boiler seems to ease itself in gently and then build up heat if required. Certainly it seems to work very well with evohome as my house is very open to west winds so part of the house is naturally warmer than other parts, yet each Orion seems to stay at the requested temp.
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Originally posted by fergie View PostMy boiler is in the garage so not that easy to sit and watch all the time. It’s a pity there doesn’t seem to be an easy way to produce output logs.
Anadotaly my boiler seems to ease itself in gently and then build up heat if required. Certainly it seems to work very well with evohome as my house is very open to west winds so part of the house is naturally warmer than other parts, yet each Orion seems to stay at the requested temp.
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Hi Hengus, I’ve checked a few times and seen exactly the same behaviour - but could be due to the hot water being on.
Evohome is controlling the zones perfectly and holding perfect temps, but the boiler seems to sit around 70 deg - even when the return is in the 60s.
It’s a real shame if Honeywell can’t find a solution to allow us to adjust the control or allow the boiler to take back control.
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Originally posted by fergie View PostHi Hengus, I’ve checked a few times and seen exactly the same behaviour - but could be due to the hot water being on.
Evohome is controlling the zones perfectly and holding perfect temps, but the boiler seems to sit around 70 deg - even when the return is in the 60s.
It’s a real shame if Honeywell can’t find a solution to allow us to adjust the control or allow the boiler to take back control.
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Joining the evohome plus atag via opentherm club today. Thanks for all the info in the post it's been very helpful in making a decision.
Any tips for wiring in the ot bridge? Doesn't seem to specify a polarity on the connections?
Do you use the external wired temperature sensor? Is it necessary for correct operation with evohome?
Thanks
Russ
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To connect via OT, you need the following part: Connector OpenTherm (Blue) 1 S4745000. There are no polarity issues with the OT Bridge.
I have HW priority with hot water demand controlled by Evohome via the HW Kit and a BDR/zone valve. Opening the zone valve, informs the boiler that max heat is required for hot water heating.
There is no need to fit an external weather sensor. Evohome does all its calculations using information from the various temperature sensors that you have set (eg; HR92, remote sensor or Evohome).
PS: Most of the information that you need is in the IS24 Servicing and Installation Guide which is on the Atag website.
Use an Atag installer if you want the 10 year parts and labour warranty.
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