New boiler - cold radiators

FreeBear

kittennose said: We have no weather comp or open therm enabled (we've had 2 plumbers over who claim it's "pointless" - my translation is they have no idea how to do it). 

OpenTherm is very much worthwhile (as are the proprietary versions from the likes of WB). An OT thermostat will throttle back the boiler if the house only needs a little bit of heat to maintain a set temperature. As a result, the boiler isn't firing up at full power where efficiency is at its worst. Instead, it is running at a lower output which translates in to a higher efficiency, reduced gas consumption, and lower fuel bills.

Same for weather compensation - When it is mild outside, the heat losses are not so great, and you don't need boiling hot radiators to lift the temperature inside. As the outside temperature falls, increasing the flow temperature means the house will heat up at the same rate at the expense of a lower efficiency. But in most parts of the UK, we don't really get prolonged periods of arctic weather, so don't need high flow temperatures to compensate.

OpenTherm, weather compensation, and smarter controls are pretty much a requirement when installing a new boiler. All part of a drive to reduce the nations gas consumption. And at the end of the day, the home owner benefits through lower energy bills.

kittennose

cheme7676 said:

Hey @kittennose - I'm facing the exact same issue after just replacing my boiler with a brand new Viessmann Vitodens 050 35kW. Rads are taking many hours to warm up.

I was wondering if you managed to find the problem? The only thing I can think about these boilers is that they allow for 'Weather Compensation' and hence run on a 'heating curve'. Still trying to figure out how to change this

Quick update:

This weekend I realised the installers must have switched the direction of flow. After having so many issues with my rads losing balance, going cold and taking 1-2 hours to heat up, I opened the flow side fully and balanced the return side and it's made a world of difference. 

We have no TRVs so both ends of the rads are the same but we have been opening the flow side fully which we now realise was the outlet! 

I was told on my rads it wouldn't matter which side was fully open but clearly it does because instantly our rads now heat up fully in 15-20 mins (rather than 1-2 hours) and are significantly quieter.

FreeBear

kittennose said: We have no TRVs so both ends of the rads are the same but we have been opening the flow side fully which we now realise was the outlet! 

I was told on my rads it wouldn't matter which side was fully open but clearly it does because instantly our rads now heat up fully in 15-20 mins (rather than 1-2 hours) and are significantly quieter.

You'd have thought it wouldn't make any difference as to which side is flow or return...

But, with a new boiler, the installer should have fitted TRVs to all radiators. It is a requirement for Building Regulations. Now that you know which is the "hot" side, mark each radiator for the day when you fit TRVs.

pieroabcd

FreeBear said:

ThisIsWeird said: Would you ideally choose, say, 18oC for Tr in bedrooms?
Still suggesting the IR Therm. 'click' - there you go

The difference between 20°C and 18°C is minimal, and only equates to a change of 0.6°C for Td. Balancing radiators doesn't have to be exact, and a +/- 1°C is well within the margin of error. Close enough is good enough.

Whilst IR thermometers are handy, they don't do well aimed at small pipes, especially if they are shiny. When I've used one, it was a bit hit & miss.

I noticed that with my ex-IR reader the reported temperature varied wildly on the pipes, by 5-10 degrees, at the point of being totally random. On top of that I've always been frightened by the risk to the eyes, so I let my fear drive me and returned the stuff.
I don't trust cheap imported stuff to respect the power limits that we have.

pieroabcd

kittennose said:

cheme7676 said:

Hey @kittennose - I'm facing the exact same issue after just replacing my boiler with a brand new Viessmann Vitodens 050 35kW. Rads are taking many hours to warm up.

I was wondering if you managed to find the problem? The only thing I can think about these boilers is that they allow for 'Weather Compensation' and hence run on a 'heating curve'. Still trying to figure out how to change this

Quick update:

This weekend I realised the installers must have switched the direction of flow. After having so many issues with my rads losing balance, going cold and taking 1-2 hours to heat up, I opened the flow side fully and balanced the return side and it's made a world of difference. 

We have no TRVs so both ends of the rads are the same but we have been opening the flow side fully which we now realise was the outlet! 

I was told on my rads it wouldn't matter which side was fully open but clearly it does because instantly our rads now heat up fully in 15-20 mins (rather than 1-2 hours) and are significantly quieter.

generally if you touch the base of the 2 pipes the flow pipe gets much hotter (and much more quickly) than the return pipe.
You can't even count on the left pipe being always the flow and the right being the return or on the TRV being mounted on the return instead of the flow (in my house there'e every possible combination, for example. Only touching the pipes helped me to sort out my problems)..