dmachado said:
I did get the idea from these types of pumps... I just spent 1/3 of the cost of these Grundfos pumps and I got the same results. My house doesn't have a recirculation pipe but it works anyway...!
I plan to do the same - it's on the big long list of worthwhile jobs. Simple manual systems or ones based on a timer or thermostat to finish the cycle and using the cold pipe as the return pipe have been used for decades in North America.
I inherited a nearly new Rinnai instantaneous gas water heater when I bought my current house. It is clearly a well made, durable unit and highly efficient at moving the heat from combusting gas into water, but...
I wanted to take advantage of the Preheat button on the Rinnai wall controller, but it does not work with third party pumps like the Grundfos, only with Rinnai's proprietary system, and that requires a return pipe from the far end of the house. My property is a 112 year old villa with four extensions and five different roof spaces, so that just isn't practical. And then there's Rinnai's exorbitant expense for their proprietary system. And it isn't energy efficient in its implementation...
The heater is designed for Japan with an efficient 100 Vac switch mode power supply. For Australia, the unit is fitted with a roughly 60 VA E-core 240 to 100 volt step-down transformer that sits there burning away about 6 watts day and night like the light bulb in a teenager's bedroom. Calculated from my data logging, 94% of the electricity used by this unit is standby wastage, about $25 per year at my current cost. For a dollar more at the time of manufacture, they could have used a toriodal transformer and cut that wastage by 90%!
The heater has a cool down cycle when water flow stops. The purpose of this is to "purge the combustion chamber" but it defeats my wisdom and it is not explained why in the owner's, installation or service manuals it needs to run for 65 seconds, a couple of seconds would be enough. The result of the cool down cycle is that you ALWAYs have to draw off cold water even if you have only a minute before been running hot water. With the hand basin in the bathroom just 2.5 meters from the water heater (as the crow flies), this takes 30 seconds! (There is a lot of pipe in the heater exchanger in addition to the pipe between the heater and the basin.)
Insulated pipes are a waste of time, because drawing off the cold water from the cooled down water heater chills the pipes anyway!
What kind of moronic thought processes are behind designs like this?
Posted Tuesday 10 Jul 2012 @ 12:37:17 am from IP
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