CH target temp

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Moved into a new house. CH seems to work, in that all radiators get warm, but they don't get hot.

Checked the boiler (Vaillant ecoFit pure) and the target temperature was set to 55.

This seems low, what should it be?
 
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For colder months as it suggests there, yes 75.
 
It really depends on how quickly you want to heat the rooms up.

The lower temperature will be more efficient.

You could also look into getting weather compensation fitted so this will get adjusted automatically.
 
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I thought I heard that 60C was the most economical condensing temperature?

and you only need to turn up the heat if your radiators are not big enough to keep the house warm in cold weather.
 
I thought I heard that 60C was the most economical condensing temperature?

I read below 55C, but the cooler the more efficient. Nowt much you can do about heating water, it has to be several degrees hotter than the temperature in the cylinder, to be able to transfer heat - so when heating water, mine is set to max - 75C I think. The rest of the time it works in conjunction with the outdoor sensor and compensation system.
 
I thought I heard that 60C was the most economical condensing temperature?

and you only need to turn up the heat if your radiators are not big enough to keep the house warm in cold weather.

It depends how low your boiler can modulate and the size of your radiators.

If you had massively oversized radiators you could easily run the whole thing at a delta t of like 30 or lower.

This is one of the most common errors of undesigned heat pump replacements where the heat pump itself will not work cost effectively at a delta T of 50 or even that age old "stick a massive boiler on it!" style work where for most of the year 30KW of output isn't required and the boiler can only modulate down to 9KW. Resulting in most of the energy going out the flue.

It's just not efficient.
 
I thought I heard that 60C was the most economical condensing temperature?

and you only need to turn up the heat if your radiators are not big enough to keep the house warm in cold weather.

Return temp of 45 is when boiler will perform to efficiencies of 90%+.
 
I had problems with mothers house, in her case a Bosch boiler, but the problem was return water too hot, and this auto turned down the boiler. It seems the idea is the TRV controls the temperature of each room, and once all rooms are warn the TRV's will all be closed so the by-pass valve lifts and hot water returns to boiler first turning the output down, and then it starts to cycle off/on.

However if any lock shield valve is wide open, that will also cause hot water to return and the boiler with turn down, so what was happening was it was heating just one room at a time, once the room was warm the TRV would close and send warm water to next room.

So the setting of the lock shield valve is very important, it seems one should measure water temperature in and water temperature out and there should with TRV wide open be around 15°C between the too readings, I tried but the thermometer idea seems good in theory but in practice could not get a steady enough reading.

So I turned off each lock shield valve in turn starting closest to boiler, allowed pipes to cool, then opened ¼ turn at a time until I felt a little warmth on the feed pipe, then went to next.

Returning to first radiator it was now quite hot, but some were still cool, so had to tweak each one ¼ turn more or less. This was much improved, but not spot on, to try and get it better I got some electronic TRV heads, these have the target and current temperature displayed Flat Battery TRV.jpg so I further trimmed the lock shield if after running for some time target was under current I would close a tad, and if other way open a bit, the problem was old TRV heads were marked *123456 which is about as much good as chocolate fire guard, once I knew the TRV was set correct, then only one thing to set, the lock shield, I actually moved the electronic head from radiator to radiator, once set the old mechanical was OK, around 2.5 = 20°C.

Once all were set, when boiler first fired up the water was hotter, and all radiators heated together, I was really pleased with how the TRV heads worked.
 
It sounds like you encountered a situation where the lockshields provided very little valve authority.

This is very common and essentially a tiny turn from fully closed allows a massive amount of flow, effectively meaning it's fully open for most usual radiators.

This makes balancing a nightmare, as often the correct flow setting will be almost no turn at all.
 
Moved into a new house. CH seems to work, in that all radiators get warm, but they don't get hot.

Checked the boiler (Vaillant ecoFit pure) and the target temperature was set to 55.

This seems low, what should it be?
It should be as low as you can get it whilst keeping your house warm if you want best efficiency. You shouldn't ask "are my radiators hot?", you should instead ask "are my rooms warm?". If your rooms are warm with radiators set to 55, they don't need to be any hotter
 

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