I have a reasonble amount of experience using these exact pumps and have a lengthy story to tell so better grab a beer. :chug:
Firstly these are hot water recycling pumps designed to pump hot water around. Don't quote me but I was told they are used in solar hot water systems to pump the water, not 100% sure of how the solar hot water system works so won't even try to go into it.
With my experience they do work but they will not last unless you use them nicely. Don't try to pump from way down low to way up high with them, it can work though if you make sure it gets primed and starts pumping ok, otherwise you can be in for a fire and burnt out pump if you just switch it on and either walk away or just stand there like a stunned mullet looking at it going but nothings happening.
So when using it make sure its pumping nicely and keep a eye on it. Also try not to pump up to high with it.
I had a couple that did work really well for awhile using them for recycling the wort through a heat exchange system during the mash and pumping through a wort chiller after the boil.
So I guess the moral of the story is be careful with it and don't try ask it to do what its not to designed to do and it will work perfectly. There a few brewers here that will tell you they we're there when one of my grundfos pumps caught fire at a all grain mash demo at a certain brewstore. Only real problem that day was the difference between how low to the ground the pump was and how high it had to pump to, also the right attention was not paid to making sure the pump was flowing proberly before just standing back and letting it go.
I guess those kind of rules for watching and treating a pump properly go for all pumps not just the grundfos.
Anyway I'am a little incoherent so don't know if I covered everything, if not shoot questions.
Alcohol fueled brewtality.
Jayse
EDIT PS here's a pic of one of mine, the one up top, also had one which was a gold colour but the very same, three speed grundfos.
h34r:
