On Friday, 6 January 2017 21:00:27 UTC, John Rumm wrote:

So this is a hammer in the CH primary system, not in the DHW take off
from the cylinder?

Has it always done this, or is it new?

What is the set point temp on the cylinder stat?

What kind of circulator pump is it? (and what speed is it set to?)


--
Cheers,

John.

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Thanks for your interest, John.

1) I *think* it's in the CH primary - hence me planning to try depressuring the hot water side and let it go through a heat up cycle to be certain.

I would say for definite that the cylinder HW outlet is not affected by vibration. Trouble is the noise is of a pitch, and reflected around in an airing cupboard, that makes it hard to localise - except by touch.

By touch I can say CH inlet and outlet to the cylinder affected equally, cold feed affected sometimes.

2) The noise issue has (I'm told) re-occurred from time-to-time over the 12 years (approx) of usage. Allegedly no problems in the early years, but has come and gone spontaneously after that.

3) Cylinder stat set to its mid-point and what I would describe as a normal domestic HW temperature at the tap (sorry, no thermometer immediately available).

4) Circulator pump is built into the boiler (Ideal icos) and is non-adjustable single-speed.