Boiler

[DerbyBorn]

After lots of checking a Heating Engineer has decided a mate's heating system has a partly blocked boiler heat exchanger. Likely? 12 - 15 years old. Has been pressure cleaned a couple of years ago.

[alan_m]

Limescale build-up? Is the boiler kettling or making other noises.

If so a dose of boiler noise reducer or anti-kettling additive to dissolve the limescale may be worth a cheap gamble for curing the problem.

[charles]

I live in a hard water area and my boiler was installed in 1988!

[John Rumm]

Could even be the result of power flushing if not done with care (i.e. remembering to take the boiler out of circuit prior to flushing so you don't end up flushing crap into the HX!)

[Tim Watts]

Quite possible in that timescale - the heat exchanger sees mains water all the time, so hard water will scale it up.

[Tim Watts]

PS pressure cleaning will not fix the potable side of the heat exchanger.

You'd have to take it out and soak it in descaler for that.

But it's easier just to shove in a new unit at that point assuming that is cost effective.

[Bob Minchin]

Quite likely designed before boilers starting having low volume heat exchangers. Keep it going, any theoretical inefficiency will be offset by the cost and relatively short life of a modern boiler.

[John Rumm]

You are assuming its a combi, and in a hard water area as well... I was assuming he was talking about the main HX being (partly) blocked on the primary side. Perhaps the OP could clarify?

[DerbyBorn]

John Rumm wrote in news: [e-mail]:

??It is a conventional Boiler - not a Combi

[Tim Watts]

Oh - yes, main HX... I just read it as the DHW HX.

[Tim Watts]

Understood - in which case, has the plumber tried a chemical flush? (Non disruptive and low risk - inject one of these:

run for the recommended time, drain and refill.

[tabbypurr]

Boiler blockage seems unlikely then. Flow failure is more likely to be down to crud in the pump impellor or settled at the lowest points in the system.

You can get a chemical that blocks holes in heat exchangers. You can run that for 14 years in a system with no filter, where the boiler kettles each time it runs and still not block the exchanger.

NT

[DerbyBorn]

New pump fitted last week. Old one was fine.

[John Rumm]

So presumably non condensing at that age... What make and model is it?

[John Rumm]

If you still have the old pump, then you could use it to lash up a power flushing system to try and clean the boiler. You would need a large tub for the water and some system cleaner, then some pushfit etc to allow you to pump directly through the boilers flow and return while isolated from the rest of the system. Should be possible with a few changes of direction to clear most blockages (unless its a spanner (literally) in the works!)

[DerbyBorn]

John Rumm wrote in news:W- [e-mail]:

Potterton something or other. I think he has committed to a new boiler.

[harry]

Unlikely. But "silt" (metal oxides" could have wafted in from elsewhere in the system. Should be easy enough to dislodge if the boiler was taken outside and the garden hose applied to the connections.

The radiators could need the same treatment. If there is a lot of crud inside, it points to corrosion problems in the system, the radiators may all be shagged.

Benefits of anticorrosion treatment in the system. Made worse if the system has been "pumping over.

[DerbyBorn]

The Heating Engineer has proposed a new boiler in view of the problem and its age.

Stangely - despite his website saying he fits Worcester-Bosch and Veissemann, he is proposing a BAXI Ecoblue

I guess based on ease of fit. Are they any good?

[Tim Watts]

I'd stick with WB or Viessmann - both have good reputations and I find my WB a decent bit of kit.

[DerbyBorn]

Tim Watts wrote in news: [e-mail]:

Unusually - the Baxi claims to not need an over-run on the pump.