Water temperature fluctuations while showering - Beneteau Oceanis 40

[AFKASAP]

Hi there,

I recently purchased a 2008 Beneteau Oceanis 40. There is a fluctuation in the water temperature. I like a hot shower, so when I put it on hot it ranges between hot and boiling. If i set it to warm it will fluctuate between hot and warm.

I think it is to do with the water pressure/pump/accumulator. Is this normal or is this the early signs of perhaps the accumulator or pump pressure sensor failing? Or something else? It is a Johnson pump.

Call me fussy but, I want a consistent water temperature when I shower.

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[dlymn]

Modern pumps have a pressure control valve that keeps the pressure uniform. If your unit has one, then it might be faulty. Have you tried turning on the shower and then going next to the pump to check to see if it's cycling on and off? Another person could feel the shower temp and tell you so that you can sense if the cycling coincides with temperature fluctuations. Are there other people on the boat? Maybe they turn things on and off when you're in the shower. Some accumulators have a pressure diaphragm that needs to be pumped up with a tyre pump in order to keep it working correctly. If yours is like this then you might pump it to see if it affects the cycling.

A new pump $60-80

[AFKASAP]

The pump does not run continously when the shower is running. But as far as I know that is normal. However I think it does not kick in soon enough.

No one else is using the water at the same time.

The temperature fluctuation does coincide with the pump cycling.



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[AFKASAP]

Photo of my setup.

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[sailorchic34]

Originally Posted by AFKASAP

Photo of my setup.

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Interesting. It appears that the accumulator is installed on the suction side of the water pump. it does no good at all there. Please verify that the accumulator is connected to the discharge side of the pump where the pex manifold is located.

[a64pilot]

t's on the pressure side, it is a goofy install though, the hose goes over the top and back to the left to get to the manifold, I had to look a couple of times as it is unusual

[AFKASAP]

Thanks. I was about to investigate.

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[AFKASAP]

Does anyone know what kind of accumulator it is and if I need to or can do anything to improve its performance?

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[Sailmonkey]

The manifold is on the suction side, it's there to select tanks to draw from.

The accumulator has a Schrader valve on top, you can add air with a bicycle tire pump, or check the air pressure in it.


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[sailorchic34]

Originally Posted by AFKASAP

Does anyone know what kind of accumulator it is and if I need to or can do anything to improve its performance?

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The problem is more piping related. That is there is fairly high friction loss in the cold side, so that as the pressure drops more hot water flows from the hot side then from cold water from the cold side.

Part of that is due to hot water having less friction loss per gpm per foot of pipe then cold water.

The best fix would be to install a pressure balanced or thermostatic shower valve. That will stop the temperature fluctuations at the shower head. Delta, T&S Brass, Symmons, etc all make pressure balanced valves and you can get one at the hardware stores anywhere in the US or amazon.

Delta Classic Chrome Single Knob Pressure Balanced Shower Control w/ Valve D044V - - Amazon.com

[AFKASAP]

Thanks sailorchic I will check out the pressure balanced valve.

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[Lepke]

If the previous solutions don't work, look at your water heating and plumbing system. If you have a quick recovery system with too small accumulator, expanding hot water can flow back into the cold. Either thru your shower mixing valve or where cold comes into the tank. So for a time you can draw hot plus warmed cold water. Check valves can help.

[sailorchic34]

Originally Posted by Lepke

If the previous solutions don't work, look at your water heating and plumbing system. If you have a quick recovery system with too small accumulator, expanding hot water can flow back into the cold. Either thru your shower mixing valve or where cold comes into the tank. So for a time you can draw hot plus warmed cold water. Check valves can help.

Good point!

[dlymn]

All good advice.
1 check accumulator pressure. 5 psi is OK, but often when you use a guage, you release too much pressure. give it 5-10 pumps with a bicycle pump--no more.

It is possible to have a split diaphragm in the accumulator You will know this because water will come out of the schrader valve.

There should be a check valve on the feed-in side of hot water service and you need to check that this is working. There is also a check valve between the pump impeller and accumulator but if this is faulty the pump would be operating at times when no-one is using water.(cycling on and off)

The working principle is that the pump accumulates a volume of water in the accumulator which then is pushed by the extension of the diaphragm away into the water supply.
If the flow is low then the pump will stop working as the accumulator releases water. Think of the accumulator as a bagpipe bladder. The piper is pushing air into the bladder as well as pushing air out into the pipes. In your system something is not working and the bladder (accumulator) is not maintaining uniform pressure.

[Dockhead]

Originally Posted by AFKASAP

Does anyone know what kind of accumulator it is and if I need to or can do anything to improve its performance?

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What you describe is a sign of the accumulator's not working.

There could be three problems:

1. If it's the type without a diaphragm, the air in it is gradually absorbed into the water and disappears. It has to be replenished. Follow instructions for the accumulator.

2. With that Schraeder valve on it, it probably has a diaphragm. The air behind the diaphragm may need regulating. Follow instructions for the accumulator.

3. If it's a diaphragm type, the diaphragm may be ruptured. Replace if possible. If not, replace the accumulator.