Knowledge sort on hidden programming of Ideal Logic² Max Heat 15kW to extend recycling time

[cliffa]

Hi, My Ideal Logic² Max Heat 15kW boiler has been in and working since December last year. You may find posts of mine around that time about setting it up in Priority Domestic Hot Water mode in conjunction with Open Therm.

I've lived with the fact that the boiler cycles a lot when the room set temperature is approached because the boiler can't modulate down fast enough or low enough for the requested flow temperature.

Although it is not going to be perfect I would like to try to extend the off time of the cycle and am hoping that there is some hidden menu where is is possible to set the cycle time? Any pointers much appreciated.

 

[JonathanM]

I don't know of anything directly on the boiler itself, but I believe this poster might be discussing a third party controller which can combine OpenTherm with control of cycle times on an Ideal Logic.

Opentherm + SAT (smart autotune thermostat). SAT tells the boiler what to do using opentherm protocol. SAT is an integration module that runs on Home Assistant.

SAT has its own heating curves and the parallel adjustment that is proportional to the heating curve. Then SAT adds the load compensation part. This means that SAT is a Weather + Load compensator which monitors the outside and the room temperature always and carefully calculates the control Setpoint. Then, in order to apply the Low-load control algorithm,SAT monitors the boiler flow water and the return water temperatures. As a result SAT calculates the ON/OFF times in 15 minutes intervals ( SAT is also able to extend the duty cycle if the control Setpoint is too high or too low ). These two developments work tightly together in order to prevent cycling and maintain the room temperature on setpoint. Moreover SAT uses the 15 min duty cycle instead of 10 min that the most commercial thermostats use, this helps to reduce the ON/OFF times of the boiler by 50% during Low-load control.

 

[cliffa]

Hi @JonathanM thanks for the reply. I did toy with the idea of adding an intermediate opentherm gateway device to add more intelligence to the control of the boiler, but TBH I just don't want the added complication. Extending the cycle timeout is a crude fix but I'm hoping it is one that can be achieved.

 

[trojanhawrs]

What thermostat are you using?

 

[Mister Banks]

Could you range rate the boiler to a lower output?

 

[cliffa]

Hi @trojanhawrs I'm using NEST 3rd Gen. I really wish there was an option to control the minimum requested flow temperature on NEST but there isn't . Hi @Mister Banks if you know how to then yes I would also consider setting / controlling the upper output of the boiler but OpenTherm basically is in control of the boiler flow temperature / output and so the boiler does modulate down at its request. The problem is that the boiler is quite slow at doing that from initial firing and even at the lowest output (5kW) it is still too much and overshoots the requested flow temp and so the boiler cycles off.

From all the posts I read on this issue I think there is a basic flaw in the way OpenThem is implemented. Rather than it asking the boiler for a specific flow temperature it would seem better if it was a bit more basic and controlled the boiler output. Say for example asking for High / Medium / Low / Off. Then the boiler could just run at the rates it was capable of running at. When there was a call for heat the OpenTherm stat would look at the difference between actual room temperature, set temperature and outside temperate and determine if it need full output from boiler, medium or low as it approached the room set temperature.

Anyway not to deviate from the original request - please if anyone knows please perhaps DM the info. Thanks

 

[idealness8583]

Nest has very limited opentherm capabilities sadly. I used it in my previous house; ideal logic combi; but it suffered from short cycling.

In terms of opentherm, It turns out that many boilers accept the opentherm command MM=0 to modulate at minimum capacity level but the boiler doesn’t respect it. So it’s the manufacturer not implementing it properly. My current Ideal Logic Heat also suffers from it; I have a temporary workaround that seems to work well and the SAT team is currently working on a solid alternative.

If you don’t want to use any additional opentherm gateways or devices, (and I don’t blame you), I can only suggest to balance your radiators where they are pretty much open but with slight resistance to help emit the heat. And if you have an external pump then speed it up. It’s not a great solution but at least it should reduce cycling. However, I don’t know if there are any other hidden menus, so maybe someone else can help.

 

[trojanhawrs]

Can you set a target temperature band on the nest? e.g. 18-21 degrees. That would let it drop off a bit more.

 

[idealness8583]

I stopped using Nest very quickly and I don’t use Nest anymore so I can’t advise on that sorry.