Re: [Amel Yacht Owners] Re: Alternating hot and cold water in showers

Ryan Meador

I don't know if it's stock or not, but my boat has a pressure regulator downstream of both the pump and the accumulator.  It's a tiny thing in between where the accumulator is spliced in and the line splits off to flush the desalinator.  The effect is near-constant water pressure (it dips for a moment when the pressure drops below the regulator set point, then the pump kicks on almost immediately), and no variable-speed pump required.  It works really well.

I have a water temperature problem of my own: my shower will be a constant temperature while it is actively spraying, but if you pause for a few seconds, the temperature changes.  In the aft head, it gets hotter (as if it were set to full hot).  In the forward head, it gets colder (full cold).  My best guess is there is some backflow involved, but I haven't figured it out yet.  It's not high on my list of priorities... it is just a split second of the different temperature before it goes back to normal.  Could what you're seeing be this, Philipp, or is this unrelated?

SM 233 Iteration
Boston, MA, USA

On Mon, Mar 19, 2018 at 9:49 AM, greatketch@... [amelyachtowners] <amelyachtowners@...> wrote:

The alternating hot/cold water problem is very common on many boats.  The usual cause is the constantly changing water pressure when you have a on/off pressure switch on the supply pump.  The accumulator tank helps, but really all it does is slow down the rate of change by allowing the pump to cycle more slowly. You'll know right away off this is the issue, because the temperature will change "in time" with the pump cycling.

A couple of things you can do that might help:  Most of the water heaters on Amels have a "tempering valve" on the outlet to bleed cold water into the hot to control the temperature.  If that is acting up, it is possible the temperature of your hot water is not constant, which would cause the problem.

If you have a tempering valve, adjust the temperature on it as low as you can.  Typically people set these WAY higher than they need to be.  If you set it just a bit hotter than you want for a shower (maybe 40-45C/105-110F) you'll find the shower is much better behaved.

Don't use the shower with the cold water "full on" and a trickle of hot to adjust the temperature.  Set the flow rate just a little lower than "full on" and the temperature will change less as the pressure cycles.

The only complete fix I know of is to switch to a pump with a modern variable speed drive that keeps a constant water pressure.

Bill Kinney
SM160, Harmonie
Moraine Cay, Abacos, Bahamas

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