Should I get opentherm concidering the risks?

[Ltnman]

I doubt the leak is be a nail.
Expansion / contraction would have pulled the repair long ago.
I would be getting prepared to have to find it and do a proper repair when you put in a new boiler regardless.

I would be looking at why your system can't do its job properly. You've a big boiler so either the controls/configuration isn't right or you live in a barn.

I would then do a system review before buying anything. Look to the modern way of heating controls (full rad control with wifi/App controls) and work backwards from what you want to get a system you will like.
Most new heating contols (Wiser, etc) seem to have opentherm or other compensation technology built in, so it's plug and play really.
Once you specify your job properly, you may find opentherm isn't needed.

The 4 bed detached house built in 1990 has dot and dab dry lined walls. The ground floor is in microbore while upstairs is in conventional piping. I note your comment about doing a proper repair to the pipe but this would be extremely hard to find so I would rather not rip the house apart unless the leak came back.

You mention why my system can't do its job properly but it works fine for me so I think it is. The gas engineer fitted a 42Kw boiler as I said I wanted a good hot water flow. The house has 11 radiators including 5 doubles plus two towel rails . It was only years later that I figured out that the cold tap was running at 12 L/m. Seems the boiler installer didn't bother checking so over specified the boiler. I think he had only just come out of training school.

 

[DP]

The gas engineer fitted a 42Kw boiler as I said I wanted a good hot water flow

So both of you share the blame then

 

[BlueLoo]

The 4 bed detached house built in 1990 has dot and dab dry lined walls. The ground floor is in microbore while upstairs is in conventional piping. I note your comment about doing a proper repair to the pipe but this would be extremely hard to find so I would rather not rip the house apart unless the leak came back.

You mention why my system can't do its job properly but it works fine for me so I think it is. The gas engineer fitted a 42Kw boiler as I said I wanted a good hot water flow. The house has 11 radiators including 5 doubles plus two towel rails . It was only years later that I figured out that the cold tap was running at 12 L/m. Seems the boiler installer didn't bother checking so over specified the boiler. I think he had only just come out of training school.

I'll answer because the Pro's just seem to want to victim blame and snipe....

Regarding doing the job properly, you have the same amount of rads as me. my 15kw boiler heats the house up easily, however its a std old, boiler (75c) so perhaps the rads are outputting more than yours would. You said it can't heat the house up in two hours.
That being the case, is that a problem? I thought it was. If so, how can you increase the heat output to get you at temp properly?
Have a careful look at the controls you are installing. My wiser system has "Comfort mode" setting in the app. This has the system self monitor heat loss and gain and allows you to set a time for the temperature to hit the set point, rather than simply switching on the heating at a set time. Works very well.
Installing a big combi boiler without checking the incoming flow rate is a **** take huh.
Not unusual by all accounts. the industry is a sham.

 

[sxturbo]

Just read your 1st post again.

The opentherm will crank up the boiler to its max to get the house upto temperature, it will then once it gets close reduce the heat demand. The idea is, that once the building is upto temperature, the boiler only needs to operate at low output and the temperature of the water will be very low keeping the boiler in condensing mode.

Boilers can be range rated, some boilers the opentherm doesn't overide this others I think can be over ridden.

My house (well insulated 4 bed semi, dot and dab walls) takes around 30-45 mins to heat up from 18 to 21 degrees, the initial water flow temps are 75 degrees, once upto temp to keep the house at 21 If we are in I've seen the flow temp be as low as 30 degrees.

Typically however our heating comes on at 6 and is off at 8, during the day the house doesn't drop below 18 degrees throughout the day on the coldest days without the boiler being on, then the heating is back on at 4.30 ready for a toasty house when we walk in at 5pm. The heating is then left on till 9, but in that time it keeps the temps through the rads around 50 degrees in the height of winter.

If you were to install a new boiler, they will do a flush of the system and its likely your leak will come back.