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Initial experience with a recently-installed Shurflo WhisperKing water pump showed it to be much quieter than other diaphragm type pumps, but hardly quiet enough to warrant its description – nor price. I eventually raised the matter with Shurflo’s technical staff in the USA, resulting in some valuable advice that is valid for all such types of pump. The pump is now inaudible a metre or two away.
So-called positive displacement pumps have a rotating motor-driven cam that drives a flexible diaphragm up and down, typically operating three separate chambers. These chambers draw water into them as the diaphragm moves downward and are closed as it moves upward. This action forces water outwards through further valves. Each chamber is pumped about 60 times a second. Inevitably noise is created through cam action, diaphragm movement, water turbulence and the drive motor.
I was aware that overly tightening the pump’s attachment screws compresses the rubber mountings, hindering their ability to absorb sound energy, but I had not sufficiently realised the importance of having a truly rigid mounting base. Shurflo suggests you first knock on the proposed base. It if responds like a drum it’s going to worsen pump noise.
I remounted the pump directly onto a solid part of the steel chassis but another effective solution is to place a small piece of carpet between the pump and its base.
Shurflo advise to use the thinnest hold-down screws that will adequately hold the pump so I took them at their word and used high-tensile 2.5 mm bolts.
AnoTher and surprisingly effective matter is to include about 350 mm of truly flexible piping between the pump and any hard plumbing on the pump inlet and outlet. A lot of noise is transmitted via these pipes if they are unable freely to move, so don’t restrain them in any way. Ideally let them hang in free space. The difference in transmitted noise is so great that I found it worthwhile to connect each pipe using a full loop.
Also necessary, says Shurflo, is to avoid elbow fittings close to the outlet port. They cause turbulent water flow and also back pressure – both of which generate noise. Use smooth curves rather than right angle bends. Yet another cause of transmitted noise is vibration of the piping and associated fittings where plumbing passes through a wall. Use plastic foam or similar as an insulator. Plumbing can also vibrate against walls and drawers etc. It is also desirable to bleed all air from the system. Trapped air causes plumbing to rattle.
Finally, adding a small pressure accumulator dampens the otherwise inevitably pulsating water flow. The result is a firm smooth and quieter stream.
The result? The now finally installed pump makes little if any more noise than a good sewing machine. Truly.
I thank Shurflo for their technical assistance in this matter. I was previously unaware that the manner of installation could so strongly affect pump noise.
ThIs short article has been prompted by postings on the Club website regarding the probable average input from solar modules in various places and various times of year. As solar irradiation varies throughout the day, and from month to month and area to area it seems complicated: it is in fact remarkably simple to do.
It works much as does the measurement of rainfall: but using units called Peak Sun Hours rather than inches and millimetres. I’ve included a technical explanation of Peak Sun Hours at the end of this piece but it’s not necessary to read it to follow how it works.
Imagine a large open drum that ‘collects’ sunlight (rather than rain). When full, regard that drum as containing one Peak Sun Hour (1 PSH). The drum is likely to fill in one hour in Marble Bar around noon, but will take longer than that both earlier and later in the day. In a Hobart winter, filling that drum may take the better part of a day.
We have no concern about ongoing variations during the day any more than we do when a rain gauge tells us we had 100 mm overnight (and we do sometimes get that in Broome). All we need to know is how many drums got filled – because that’s the PSH for the day.
dependIng mainly on latitude and season, PSH in Australia varies from 2.0 (down south in winter) to as much as 7-8 (in central and southern areas in summer). Northern Australia has less variation: it’s from 5.5 in winter to 6.5 in summer.
The met office has maps that show PSH but you’ll need to juggle scientific units to tune the data into PSH. My books show it far more simply but I’m not really supposed to tell you that here. Better then to suggest that, for most purposes and places, to settle on 4.0 – 4.5 PSH if you mostly see a glass as half full, and 3.5-4.0 PSH if you mostly see the same glass as half empty. Turning PSH into probable watt/hours per day is truly simple. Take 70% of what you thought your modules produced (i.e. what it said on the box) and multiply that by the PSH for the area and time of interest. That’s the most probable solar input for that day for modules mounted horizontally. There will be daily variations, but the totals will be surprisingly accurate most of the time. Some gains can be made by tilting modules to face the sun, but with motorhomes it’s much simpler to have them flat or close to flat and add a bit more solar capacity to compensate.
In techo-speke (and quoting Kyocera), ‘Peak Sun Hours are the equivalent number of hours per day when solar irradiance averages 1000 w/m2.’ For example, 6 PSH implies that the energy received during total daylight hours equals the energy that would have been received had the irradiance, for those six hours, been a constant 1000 w/m2
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