Central heating questions

System

Phil3822 wrote: »

Thanks again, is there anything to say when the boiler is in condensing mode? I take it my hive set up is a simple on and off type. I was tempted by the atag one. I will play about with the boiler buttons to view readings. When am I best to do this? I don't really understand what the A3 is, is it the current water temperature rather than max which A0 shows. Nice to see a fellow atag user. I like to understand all the things in my home where possible.

A modern boiler is condensing mode when the Return Flow Temperature is less than 54C (as shown in the A1 setting on your boiler). I know that some boilers display this fact in a more obvious way. Typically, a boiler with a return flow of 54C will have a gross efficiency of 88% and a net efficiency of 98%. As the temperature of the flow return temperature falls then efficiency increases. For example, at 40C the gross efficiency may be as high as 94% with a net efficiency of 105%.

Am I correct in thinking that your boiler comes with external weather compensation? If so, this adjusts the maximum central heating flow temperature down and up depending on how warm and cold it is outside. The boiler's computer will then do what it can to achieve the maximum temperature differential between the outbound and inbound flows to maximise efficiency. Your boiler is also Opentherm capable. This protocol is now over 30 years old and whilst it is mandated for use in The Netherlands, UK installers do not understand it and boiler manufacturers promote their own controls. Using an Opentherm bridge does what weather compensation does and more. I think that I am correct in saying that the Atag One control system is connected via Opentherm as is the new Nest 3. So what is Opentherm?

Have a look at the PDF link:

https://ensupport.getconnected.honeywell.com/s/article/What-is-OpenTherm

Phil3822

Thanks for the info again. Learning lots here. I have just read the following on the boiler. A0 74c, A1 60c, A3 74c. I have the water temp for radiators set to 65c so do not understand what is going on. I assume as it is morning and starting up from cold the boiler is increasing temperature but taking it out of condensing mode while doing so.

I will find out about the weather compensator, maybe should have gone for the atag one but didn't want wired connection.

Thanks again.

System

Phil3822 wrote: »

Thanks for the info again. Learning lots here. I have just read the following on the boiler. A0 74c, A1 60c, A3 74c. I have the water temp for radiators set to 65c so do not understand what is going on. I assume as it is morning and starting up from cold the boiler is increasing temperature but taking it out of condensing mode while doing so.

I will find out about the weather compensator, maybe should have gone for the atag one but didn't want wired connection.

Thanks again.

I am guessing that your installer has not changed any of the Boiler Parameter Factory Settings (page 41 of the installation manual). He will have left it set to CH Tmax of 80C: Gradient 5: Heating Line 24. My installer did his calculations and set Parameter 2 with a CH Max of 70C.

I suspect that what you are seeing is the boiler reducing from maximum flow temp down to the flow and temperature needed to sustain your heating demand. I am not familiar with the detail of Hive but the Honeywell range of controls will demand maximum boiler heating when there is a large central heating demand. Some heating controls will over-ride user settings on the boiler. For example, Honeywell Opentherm controls do not work well with Viessman boilers. Whenever there is a HW demand, the controller demands 92C which is supposed to be limited by the boiler parameters. This works as it should on Atag and Intergas but not on Viessman. Why - because not all protocol settings in the Opentherm protocol are mandatory. Moreover, with Opentherm the CH temperature side of the control panel is rendered inoperative as Opentherm takes the decision away from the end user. The boiler flow temperature will always be as low as is needed for the system and the OAT. For example, my 19 radiators are up to their individual settings and, when heat is needed, the calculated flow temperature is 52C with a return of 40C. Most of the time, TSet Calculated sits at a notional 20C with just the pump running.

Phil3822

Thanks again, been monitoring my settings and readings. When hive demands heat the boiler pushes to deliver at max, often achieving temp over 70c and a return of around 60c max. It seems I am set up in a simple way but not as efficient as it could be. Have emailed the installer for thoughts. Maybe hive is not right for me. The boiler appears off more than it is on and just simply goes on off till temp achieved. It is ignoring my set up water temperature for radiators and hot tap water it seems. Thanks again, learning much.

matelodave

AFAIK the Hive thermosat, is just that, a thermostat but which has the ability to be remotely set or controlled.

It doesn't know anything about the boiler that it's connected to so just turns it on & off just like a cheap and cheerful Screwfix one.

System

Phil3822 wrote: »

Thanks again, been monitoring my settings and readings. When hive demands heat the boiler pushes to deliver at max, often achieving temp over 70c and a return of around 60c max. It seems I am set up in a simple way but not as efficient as it could be. Have emailed the installer for thoughts. Maybe hive is not right for me. The boiler appears off more than it is on and just simply goes on off till temp achieved. It is ignoring my set up water temperature for radiators and hot tap water it seems. Thanks again, learning much.

I have Evohome which works extremely well with my Atag via a Honeywell Opentherm Bridge. If I was looking for a new control system today, I would also look at Atag One; Nest 3 and the new Drayton Wiser. The first two are definitely Opentherm compatible. There is a review of the Wiser system on the AutomatedHome website.

Another review here:

https://www.techadvisor.co.uk/test-centre/digital-home/best-smart-heating-systems-for-2017-3583499/

Phil3822

Would I have any effect by reducing the temperature by the user interface from 65c to 60c or lower? Or because the manufacturer override is likely set to 80c my changes would make no difference. The boiler is rarely in condensing mode due to current set up. I will ask installer about atag one and consider coping with a wired installation although I want to know if the boiler override max temp is adjusted if this will help. Thanks for the help.

matelodave

Ideally you want the boiler temperature as low as possible - the hotter you run it the less likely it is to be in the condensing zone.

The balance is between getting it to run at a lower temperature and getting the radiators hot enough to heat the place within a reasonable time, especially if you run the system in an on/off manner.

You may find that running the boiler at a lower temperature but for longer will work out cheaper than just blasting heat into the house and causing the boiler to cycle on and off. We found that running the boiler a different way when we retired did make a differnce to our heating bills, actually it was a bit cheaper which sounds counter-intuitive

A lot will depend on your lifestyle and how you need to heat the place - all day, or for short periods like in the morning before everyone leaves the house and evening when everyone gets home. In the all day scenario it might be better to have the rads lukewarm all day with the boiler idling gently or hotter for a quick heat-up when you get home.

Most boilers are considerably less efficient when firing up so it's better to have it gently modulating rather than flogging away for short boosts.

You need to try and monitor your energy consumption with the boiler set at different settings although bear in mind that the weather will have a big effect on your consumption as well.

It took me a whole winter before I'd managed to tweak my present heating system to suit our lifestyle, comfort and maximise it's efficiency. It's not a combi but has lots of adjustments including weather compensation and eight zones each controlled with a programmable thermostat

Phil3822

Thanks, the point I am trying to figure out is that my boiler manufacturers overrides seem to mean my set up is ignored to a degree. At the present I am unable to make any adjustments due to pre set things I believe. I can see a couple of needed adjustments to help things to our needs but untill I receive advice from the installer i will leave and learn what I can. Been a while since posted here and appreciate the responses.

Phil3822

matelodave wrote: »

Most boilers are considerably less efficient when firing up so it's better to have it gently modulating rather than flogging away for short boosts.

This is what I want however with a hive thermostat my system will just do the on and off thing, I don't believe the boiler will modulate around the thermostat set temperature. I will await stats installation response. Thanks again.