Central heating overhaul questions

[Avocet]

My central heating system is 15 years old. It's a Worcester oil fired combi boiler doing hot water, about a dozen radiators and a towel rail. It has been serviced every other year and the boiler itself seems OK (although we've had to change a few bits in the last few years). The radiators all have thermostatic valves and there is no room thermostat. Almost all the thermostatic valves are knackered. Some won't shut off and just bake you. Others won't open (or are very reluctant to). I sometimes have to take the thermostatic head off and pull the pin up manually. One radiator is permanently cold. There's a blockage somewhere between a manifold and the inlet valve - I can disconnect it and no water comes out! The piping is a mixture of plastic and copper, all "microbore". Some radiators have slightly colder patches near their bottoms. The piping is mostly between the upstairs floor and downstairs ceiling and having cork tiled the landing, it would be a complete nightmare to try and get to the manifold!

What are my options? I hear there is a boiler scrappage scheme at present. Should we replace the whole system? Would a new oil boiler be that much more efficient than a 15 year old one? (we have no gas). Is there an effective way of flushing it? Could I put an air line on the blocked pipe to try and clear it? Is geothermal heating a viable alternative for a house without underfloor heating?

 

[muggles]

OK first things first, you've missed the boiler scrappage scheme by some way, it ended a few months ago.

Changing the TRVs is something that it sounds like you need to do, as it's every radiator a complete drain-down would be the best way to go. It's a shame you don't have access to your manifold as the completely blocked pipe would be best treated by disconnecting at either end, extending one end to outside and then applying pressure to the other end to clear it through. If you're considering ripping the lot out and starting again then that cork floor will almost certainly have to come up.

There are two options here, either go for a full powerflush to try to clear everything out, or remove it all and start again (this could either mean re-pipe only or re-pipe and new rads, but if the rads are OK other than needing flushing out there's no real reason to replace them unless you want new ones).

A new oil boiler would be more efficient than an old one but whether it would ever pay for itself is debateable. Geothermal is better suited to Underfloor although it can work with a traditional system, but it is very expensive to install.

 

[Avocet]

Thanks for that. What does a "powerflush" involve? Where I live, we have good mains water pressure (4 bar or so). If I were to disconnect each pipe in turn, fit something to the end of it to take it out of a window and open the fill valve fully, would that be likely to have the same effect as a power flush, or is that something else again?