Powermax HE85 digital pressure sensor wrong

[wilson99]

The bolier was commissioned Aug-03 and has previously had problems with the digital pressure sensor.

The analogue sensor displays 1.75 bars, switching the system on drops to 1.5 bars then locks out (A15). During this time the digital readout shows 0.1 but has also be known to raise continuously upto ~4-5 bars.

The digital pressure sensor is red, and previously when this problem occurred a guy came along spent about 10 minutes doing various things including removing/cleaning the digital sensor.

So how should I go about cleaning/unblocking the sensor - does the system need to be bleed? Or should I just get the system serviced and what sort of price would that cost?

 

[baxpoti]

As far as I know the Huba pressure sensor is not repairable, it needs to be replaced and the system probably needs cleaning!

 

[wilson99]

The small whole in the digital sensor was blocked. I used a pin to clear the path. Works again

 

[Onetap]

The small whole in the digital sensor was blocked. I used a pin to clear the path. Works again

Previously discussed here;

//www.diynot.com/forums/viewtopic.php?p=482754#482754

"On commercial systems it is normal practice to fit a syphon tube on the inlet to a pressure gauge or sensor in order to stop any debris in the water getting into the instrument. The syphon is a 'U'-shaped or 'O'-shaped piece of tube which is intended to trap an air pocket between the water and the instrument inlet. The air transmits the pressure to the gauge/sensor, but the dirty water doesn't get into it. Design fault methinks."

Is there any reason why one couldn't bend a bit of tube into a U-shape and fit that before the pressure sensor (so trapping an air seal and keeping sludge out of the sensor)?

 

[Agile]

The air would get dissolved in a sealed system after a little while.

But a domestic mass produced boiler does not have the same nice to have things that are possible on a commercial system.

The whole basis of domestic boilers is that the system is cleaned to BS 5410 before trhe boiler is fitted.

Tony

 

[Onetap]

The air would get dissolved in a sealed system after a little while.

The oxygen does, I don't think the nitrogen does.
I can't recall problems with any sensors that had a syphon fitted.

 

[Agile]

The oxygen dissolves quite quickly but the nitrogen much more slowly and to a much lesser extent.

Tony

 

[Onetap]

The oxygen dissolves quite quickly but the nitrogen much more slowly and to a much lesser extent.

Tony

The dissolved oxygen is removed from solution by the oxygen scavengers in the corrosion inhibitors or, if they have been depleted, by rusting the radiators. Then the water can dissolve some more oxygen.

Syphons seem to be effective, so I'd guess they retain the air seal. Many commercial systems, where gauges and sensors are routinely fitted with syphons, nowadays have vacuum degassers fitted, which might make the syphons ineffective. I dunno, I'll have to check now.