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Central Heating

Will i need new radiators?

Changing from a gravity fed boiler system to a new combi system, i have been advised that new radiators and pipe work would be needed. Is this the case or would the existing system be adequate? The current radiators are fairly new with the exception of one or two.

2 Answers from MyBuilder Heating Engineers

Not necessarily but the installer will be taking responsibility for the entire system.
There may be quite a lot of rust damage inside the radiators and sludge built up in the pipework. More importantly, the system has never been under much pressure (prehaps 0.6bar for a 2 story house) and the combi will have a far higher operating pressure (around 2.5bar).
Personally, if you said to me you wanted to keep the old rads/pipework, I'd write an exclusion into my quote so if there was any trouble, I wouldn't be liable.
The installer should be pressure testing the entire system at 1.5 x operating pressure (different for plastic pipe) for at least an hour before he leaves but many don't to save time. If it's properly tested, it will be very unlikely that you'll have a problem.
There may be other reasons to make pipework adjustments for efficiency sake, this is very difficult to comment on without seeing it. For example some gravity systems on the one-pipe method will not work with thermostatic valves and are obscenely inefficient.


Answered 18th May 2015

Generally no your existing radiators are fine as long as they are in good order and not damaged/rusting etc as changing from a gravity system to a pressurised increases the pressure inside the radiators and will highlight any weak spots causing a leak. Your pipework should be fine also but make sure that the system is flushed to clean it out before fitting a new boiler (you wouldn't fit a new engine into a car and then use the old oil out of the old engine!) Also flushing the system will also identify any problems as the system is flushed under pressure so weak spots will show themselves.
I hope this helps


Answered 18th May 2015

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