Ok. with cold water how often do you callibrate the pressure ie. alter the pressure setting? Hardly ever I bet - maybe alter the flow now and again possibly tweak the pressure in the winter.
Now, when you start swapping between hot water and cold water then you have to start chasing the pressure setting to match the temperature because your hose will start to soften and swell with the heat - your dead end pressure becomes too high.
If you have a modern digital controller then when in dead end it will flash for a while then add more pressure as the hose expands. When its in dead end mode it's a right pain to hold down two buttons, wait for the display to settle and alter the callibration, switch off and restart.
With a manual you simply tweak the dial when required.
The original Varistreams were crap because you had to dismantle the unit to alter the pressure. Fine if you never needed to.
I have the new one that Gardiners sell from Spring Controllers. It's pretty good but to turn it off you need to turn the flow dial down to zero every time and back up to turn it on which in my opinion is not a great idea.
The Spring controller also keeps the pumps pressure switch too so that the pump can cut the pressure as well as the controller.
The guy who makes them is often on here and can explain the reason far better than me.
http://www.springltd.co/node/67
Mark you are spot on with the calibration and DE detection will; need adjusting if you switch between hot and cold water.
The reason as you say is down to the expansion rates of the hose warm water softens the hose wall and as a result the hose will expand more than than if cold water is being used.
The change in the expansion rate of the hose will impact on how much pressure is required to get the water flowing and in turn will affect the DE detection. The answer as you say is to recalibrate the controller.
The New analogue you are using has a new micro DE retest which will also feature in the upgraded digital controller. The new micro test effectively limits how much pressure can build up in the system. Only enough pressure to allow the DE retest to take place - in short there should not be any continual pressure increase beyond this point while in DE.
Interesting point on the calibration of the analogue The quick guide suggests that calibration be done by turning the control full up (to the right) then back to the left until the water stops, finally turn right slightly.
That said the calibration would also work starting from zero and turn up (to the right)
The may be a delay with flow stopping as the control is turned down to zero, depending on your preferred calibration and pressure settings
The reason for this, is because it will take the pump a couple seconds to build the extra pressure for the control to detect.
Generally how long do you feel it takes to DE when you turn the control to zero? and what is the approx calibration setting you use? Lastly what size pump are you using?
Thanks for the feedback Mark
Ian
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