T500 Needle Valve Sensitivity Issues?

[Voddy]

I'm delighted with my T500 and I'm loving getting to know it.

However, the needle-valve is becoming an issue for me.

I have run a washing-machine water pipe from my water mains supply and I have a thumb-screw gate/switch on that pipe which controls the water flow from stop to full-on. I have that gate open just a fraction of a smidgen. In fact, I timed the water flow at that point to be around 700ml per minute. My mains water pressure behind that is around 12 litres per minute, so having that gate open a tiny fraction is important. Right now, coming into winter, my water temp is around 8-9degC.

At the other end I have another water thumb-screw gate/switch so that I don't have to keep bending down behind the counter top to turn off the water. And from that counter top end I have got my needle-valve to my T500 water in.

Here's the rub: a turn of less than 1mm (yes, 1mm) makes a temp swing on the T500 output of around 4degC; I can go from 55-60 in less than 1mm of a needle-valve screw turn.

Ideally, I would have loved to be able to make say half-a-turn for a 1degC difference.

What do you guys think? Anything I can do more?

[YHB]

You have too much water pressure, controlling the flow rate wil not alter the pressure.

There are devices known as Pressure Reducing Valves that will help. They do two things.

1) reduce the pressure to give you more control

2) Stabilise the flow so that it minimises the effect of someone flushing the loo or having a shower.

There are a few threads about them - use the search function with "Pressure reducing" as the topic.

Otherwise here is one that will get you started

viewtopic.php?f=12&t=982&p=7553&hilit=pressure+reducing#p7553

I have not needed one with my set up, so I have never bought one but I see lots on e-bay amazon.

Toodlepip

Brian

[vino-tinto]

I agree with YHB, you need an inline pressure control valve. My water pressure shows 4 bar so I have set the valve at 1 bar that way no increase or drop in water pressure has any effect.

The other problem is the size of the knurled screw on the needle valve, so I got a piece of plastic pipe that squeezed over it tightly and glued that to a 3" round knob.
The bigger the diameter makes it easier to make minor adjustments, I put marks on it to have a visual guide also

[Superslim007]

I agree got the same valve as vino there not much on Fleabay

[Voddy]

You guys are super - thanks a bunch.

I'll go off and get one asap. Never heard or known about them before now - hence not searching for that term.

[Luckyshot]

Hi All

I got a PRV from Toolstation for about £20.Once the still settles down I dont have to adjust the needle valve very often, even with the PRV the needle valve is still very sensitive,but you get used to it.

[vino-tinto]

If you cannot get hold of a bigger knob, try getting a piece of tubing that is a tight fit over the needle valve knurl adjuster, leave it proud by an inch, put a 3" nail or something like through it, it gives you a visual position like a clock hand, but you can adjust it with greater accurancy

[Admiral Toad]

Similar to VT I epoxied a 21/2 " nail to the wee knob works a treat together with pressure reducing valve

I also use a probe thermometer bought off eBay with adjustable high and low temperature alarms very usefull

[John51]

I have my pressure valve fitted inline with plastic water inlet on the still head.

What I haven't been able to find online is an exploded diagram of how it works. Not that I'm a machinist but I'm curios.

For our purposes, we don't need the dial or any adjustments, something made with abs and stainless to give somewhere between half and one bar would be enough, as long as it was consistent.

[YHB]

First diagram is indicative of how they work.



Second one is more realistic of how they are made.

[John51]

Thanks for that. Quite simple really, higher pressure moves the bellows therefore lowering the pressure.