It's to do with cavitation. At temp's over 65 the water will tend to cavitate and that will have two results... poor hot flow to the shower and possible a damaged pump.
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20 years ago
shower pumps and 65 degree celcius
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20 years ago
Hi, I am in the process of installing a shower pump and while I was researching the ways and means I kept coming upon info that said the max temperature on the hot water side was 65 degrees C. Is that a legal/standards requirement (to prevent scalding if the cold failed) or is it a limitation on the pump (cavitation or somesuch)?
Does anybody know? If so please share your knowledge.
tia, Ken remove 'spam' from email to reply
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20 years ago
Quite frankly, if your DHW temperature is above 65C, you need it fixed.
Christian.
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20 years ago
One reason those with pumped showers are tempted to increase the temperature is that, when the shower mixer tap is set for equal amounts of hot and cold (and usually, therefore, for non-thermostatic mixers, also maximum flow), the shower is too cold. Increasing the temperature above 65C does make the hot taps somewhat dangerous though! Personally I have mine set at 65C for the first reason, and no higher, for the second. Decent manual shower mixers (like the one I have) have insertable endstops to limit the travel in the hot direction to prevent scalding.
To take up on another point of the OP, it should be impossible for the cold to fail before the hot if the shower has been installed properly (at least in a "conventional" vented DHW system) - the shower should have a separate cold feed from the header tank, taken from a point below the take off for the DHW. This means the hot always fails first.