New Boiler - Maximum Temperature Issue?

[Searcher2]

I've had a new Vaillant Ecotech Pro 28 fitted in a holiday let this week to replace a Ferrolli F30. All seemed wonderful - very quiet as I hoped. It's controlled by a Hive and after he installed it I set the temperature up high on the stat. The 'Hive' recorded temperature rose as expected but then struggled to get to 20C. When I contacted my installer he said that he had set the radiator temperature on the Vaillant at 55C.... so yesterday I went to the property and set it to 70C. However, last night it struggled to get to 21C.

15:00 18.0C
15:30 18.6C
16:00 19.1C
16:30 19.4C
17:00 19.7C
17:30 19.9C
18:00 20.1C

and then roughly 0.1C per half hour.

On the Ferroli it was set to 70C and would manage about 1C increase per hour (as the Vailllant does getting up to 19C) to about 23C and then slow down the increase to reach a maximum of 25C. It's fine at low temperatures e.g. this morning it was 15.4C at 5:30 and it's now (7:30) 17.9C.

I know it's cold outside but I don't think it's any colder than it has been over winter and I would have thought a 15C increase in output flow temperature should have resulted in a more noticeable 'top' temperature.

I will be contacting the installer but as it's Sunday I am not sure when I will be able to get hold of him and as I have guests in tomorrow I am going up back up to the property to set it to 75C and see if I can check the return temperature. The radiators seemed very hot to touch. I am sure the display was showing a flow temperature of 70C too. The system configuration is the same - only the boiler has changed. If anything I would have thought it would be hotter as it's been flushed.

Any ideas what may cause this or what I should check?

 

[Sparkgap]

I've had a new Vaillant Ecotech Pro 28 fitted in a holiday let this week to replace a Ferrolli F30. All seemed wonderful - very quiet as I hoped. It's controlled by a Hive and after he installed it I set the temperature up high on the stat. The 'Hive' recorded temperature rose as expected but then struggled to get to 20C. When I contacted my installer he said that he had set the radiator temperature on the Vaillant at 55C.... so yesterday I went to the property and set it to 70C. However, last night it struggled to get to 21C.

15:00 18.0C
15:30 18.6C
16:00 19.1C
16:30 19.4C
17:00 19.7C
17:30 19.9C
18:00 20.1C

and then roughly 0.1C per half hour.

On the Ferroli it was set to 70C and would manage about 1C increase per hour (as the Vailllant does getting up to 19C) to about 23C and then slow down the increase to reach a maximum of 25C. It's fine at low temperatures e.g. this morning it was 15.4C at 5:30 and it's now (7:30) 17.9C.

I know it's cold outside but I don't think it's any colder than it has been over winter and I would have thought a 15C increase in output flow temperature should have resulted in a more noticeable 'top' temperature.

I will be contacting the installer but as it's Sunday I am not sure when I will be able to get hold of him and as I have guests in tomorrow I am going up back up to the property to set it to 75C and see if I can check the return temperature. The radiators seemed very hot to touch. I am sure the display was showing a flow temperature of 70C too. The system configuration is the same - only the boiler has changed. If anything I would have thought it would be hotter as it's been flushed.

Any ideas what may cause this or what I should check?

Probably not your boiler. If it's giving 70C that should pretty well cover it (most old systems were designed for 82/71C so mean temp of about 75C). Have you checked to see what the return temp is at the boiler when it's giving 70/75 out? What about the location of the Hive sensor? Could it be getting a cold draught? Another thing: how did you check the temperature previously or is it just that the room temp is not getting to the Hive setting?

 

[Searcher2]

Thanks for the reply. The return temperature was 65C after I set the output to 75C. I don't think it is the boiler. The hallway radiator was scorching hot and that is the nearest one to the Hive thermostat. I do wonder if the radiators are balanced.

Now that I have set the output to 75C it has managed to get to 23.7C and is edging slightly up so is performing more like the Ferrolli did. The Hive sensor is in exactly the same place as it was for the Ferrolli. Nothing changed except the boiler.

 

[Sparkgap]

Thanks for the reply. The return temperature was 65C after I set the output to 75C. I don't think it is the boiler. The hallway radiator was scorching hot and that is the nearest one to the Hive thermostat. I do wonder if the radiators are balanced.

Now that I have set the output to 75C it has managed to get to 23.7C and is edging slightly up so is performing more like the Ferrolli did. The Hive sensor is in exactly the same place as it was for the Ferrolli. Nothing changed except the boiler.

I suspect the Ferrolli was running at 82/71 so a mean temp of 76.5C. At the moment you're getting a mean temp of 70C so rads probably giving about 85% of normal output (a lot would depend on how the system and rads were sized and whether they stuck 10-15% extra on. Assuming this was with outside temp at about design conditions? (-1?)
35 years ago I'd design systems for -1C outside and 82/71C flow/return and probably oversize rads by 15-20%. Now I design them for -4C outside (whatever happened to global warming? 🙂) and 80/60C and oversize by 10%.

 

[SimonG]

Close the windows.

Would doubt its the installers problem.