When the Vokera man serviced my old boiler I asked him what
conditionthe 20 year old heat exchanger was in. he said it was fine
and he told me the usual reason the heat exchangers failed was because
of pressure fluctuations gradually causing metal fatigue as the thing
flexed. When people let the accumulator run out of air the
fluctations got bigger (hot/cold expansion) leading to rapid fatigue
and failure.

So this set me thinking - would it extend the life of the heatex to
add a bigger accumulator to reduce the hot/cold pressure
fluctations?

has anyone else heard this or is it another urban myth that these
repairmen tend to carry (the previous guy assured me I shoud leave all
the TRVs on maximum all the time for max efficiency).

Robert

In an earlier contribution to this discussion,
RobertL wrote:

When the Vokera man serviced my old boiler I asked him what
conditionthe 20 year old heat exchanger was in. he said it was fine
and he told me the usual reason the heat exchangers failed was because
of pressure fluctuations gradually causing metal fatigue as the thing
flexed. When people let the accumulator run out of air the
fluctations got bigger (hot/cold expansion) leading to rapid fatigue
and failure.

So this set me thinking - would it extend the life of the heatex to
add a bigger accumulator to reduce the hot/cold pressure
fluctations?

has anyone else heard this or is it another urban myth that these
repairmen tend to carry (the previous guy assured me I shoud leave all
the TRVs on maximum all the time for max efficiency).

Robert


I'd not previously heard that one. I would have thought that the stresses
induced by heating and cooling the heat exchanger would be far greater than
any caused by pressure fluctuations.
--
Cheers,
Roger
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On Dec 11, 4:26*am, RobertL wrote:
When the Vokera man serviced my old boiler I asked him what
conditionthe 20 year old heat exchanger was in. *he said it was fine
and he told me the usual reason the heat exchangers failed was because
of pressure fluctuations gradually causing metal fatigue as the thing
flexed. * When people let the accumulator run out of air the
fluctations got bigger (hot/cold expansion) leading to rapid fatigue
and failure.

So this set me thinking - would it extend the life of the heatex to
add a bigger accumulator to reduce the hot/cold pressure
fluctations?

has anyone else heard this or is it another urban myth that these
repairmen tend to carry (the previous guy assured me I shoud leave all
the TRVs on maximum all the time for max efficiency).

Robert

What you can monitor is water pressure to be sure its at the minimum
to run right, your system only needs enough water- pressure to get out
the air and have all water. A boiler repair guy isnt going to spend
the time to do it right they just fill it up, I got mine about 40%
lower in pressure. At the highest radiator on a cool non running
boiler bleed off some excess water. You shouldnt have much pressure
fluctuation between cold and hot, maybe 5lb, im in the US, I dont go
by bar, excessive fluctuation, or pressure raising way up when running
is another issue you dont want. Low pressure = low stress

RobertL formulated the question :
So this set me thinking - would it extend the life of the heatex to
add a bigger accumulator to reduce the hot/cold pressure
fluctations?

It only needs to be big enough to take care of the expansion. The thing
is to make sure the diaphragm doesn't burst and that air pressure is
maintained.

Wear and tear will be mostly due to heat cycling, rather than pressure
cycling - so anything which will help reduce this will improve
longevity.


has anyone else heard this or is it another urban myth that these
repairmen tend to carry (the previous guy assured me I shoud leave all
the TRVs on maximum all the time for max efficiency).

A really bad idea from a fuel economy point of view. How much fuel
would need to be wasted, to make the boiler last a little longer and
how much do boilers cost?

--
Regards,
Harry (M1BYT) (L)
http://www.ukradioamateur.co.uk