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Originally Posted by Turbokeu
Are you sure Cathar?
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Pretty sure, unless the Johnson headquarters engineer was lying to me.
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Originally Posted by Turbokeu
AFAIK (from the CM series datasheet) the CM30P7-1 has a ball bearing permanent magnet motor.
Permanent magnet motors by conception are brushless...
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Now one needs to ask oneself, what would a permanent magnet need with a ball bearing? How the CM30 is designed is that there is a brushed DC motor that spins an armature with permanent magnets on it (not electromagnets). This armature is sealed away from the impeller magnet (just like any other mag-drive pump). The spinning motion of the armature magnets turns the impeller around. I drilled the Johnson engineer long and hard on this to explain it to me in detail so I could understand just how the pump motor worked, and therefore why it was brushed.
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Originally Posted by Turbokeu
This is one of the two big differences between the CO30 and the CM30 series (beneath the direct driven vs mag driven impeller).
Couldn't find any number for the MTBF although.
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Johnson try to avoid giving out that information. The engineer told me that I could expect up to 4000hrs of life span. I went to a marine shop today and poked through their manufacturers catalog and found the CM30P7-1 listed in there with an explicit 2500hr MTBF written in the information section. i.e. Johnson's official material states 2500hrs to be safe, but their engineer reckons 4000hrs is more typical. Either way, it's still just 3-5 months of continuous use.
The engineer informed me that Johnson are looking into making a brushless DC version of the CM30, but not to hold my breath on it appearing real soon.
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Originally Posted by Turbokeu
BTW, these Laing pumps look promising, what about availability and pricing?
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All answered in the thread I linked to. Available direct from the USA division of the parent company for $95 US each. The parent company is in Germany. The US website is
http://www.lainginc.com/. Their German website is
http://www.laing.de/.
The German engineering data for the D4 pumps can be found starting here:
http://www.laing.de/10Produkte/40Pum...en/00index.htm
They are made for solar hot water circulation.