[OT] Recomendation about Reed switch

[Warichet]

Hi,

Anyone having a recomendation about high quality, reliable Reed switch ?

I've already installed some of those devices, but they tend to have problems after a year or so. Usually, the contacts stick together although they have been installed according to manufacturer specifications about the distance between the magnet and the contact. I'm looking for the classical On/Off Reed (not the impedance loaded)

Thank you

[Bainit]

Hello Raymond,
I've no recommendation about reed contacts for you.
But I think you should have a look at the rest of your installation.
A to high voltage during switching can lead to arcing during switching. In consequence the contacts will stick together.
There are to main issues that will prevent arcing in the reed.
- short wire length between reed contact and binary input device
- low voltage
Some binary input devices have a very low voltage of 5V or even 3.3V and are best to prevent arcing. I've heard also about some devices which should pulse the current.

Arcing is connected with long wire lenght because of the very fast switching of a reed contact and the fast discharge of capacity (or inductivity, I don't know excactly) on the wire.

Greetings, Sebastian

[Warichet]

Hi Sebastian,

A to high voltage during switching can lead to arcing during switching.

Thank you for bringing this isue to my attention.
I should have given a bit more information, all Reed are connected via ABB or Merten 4 fold or ABB UK/S binary inputs, I guess the voltage should not be an issue as it is pulsed from the BE.

Arcing is connected with long wire lenght because of the very fast switching of a reed contact and the fast discharge

Unfortunately, the wire length is not an adjustable parameter, indeed I've some lengths of 30m (I've seen reports where someone tested a coil of 100m KNX cable with a binary input, no problem, although no idea about long time testing results)

[lobo]

I guess the voltage should not be an issue as it is pulsed from the BE.

Hey Raymond,

I don't know for the Merten, but I doubt this for the ABB UK/S. The BE/S 4.20.1 should have a pulsed voltage.

AFAIK, you need to provide the contact voltage by yourself ... so do you use 24 or 12 V?

Cheers,

Stefan

[Warichet]

Hi Stefan,

I doubt this for the ABB UK/S.

You are right for the UK/S I did indeed supply an external 24 V.
Do you think this might be to high a voltage for the Reed lifetime ?

[lobo]

Raymond,

as far as I know, there are much more differenzes between the different possibilities to read out the reed-relays than in the relays themselves, so as Sebastian already proposed, better have a close look onto your electrical read-out.

24 V is a fairly high value ... although the given values for the allowed voltage for reeds is often significantly higer, you will get quite some trouble concerning the stored charges within your cable. There were several posts concerning this issu from StefanW (I just foundthis one).

So - my understanding would be to first look for a reed that can withstand as much voltage as possible and in the long run you should perhaps have a look onto the MDT Binary inputs. As far as I remember, they do have a fairly low pulsed voltage and they allow cable lenths up to 100 m.

Best regards,

Stefan

[Bainit]

Hello,
I'm absolutely agree with Stefan's statement.
But I want to add, that it could help to change your power souce from 24V to 12 V before switching from ABB UK/S to MDT. Does the UK/S has dedicated power sources for contacts and own power supply? In this case it could be interesting to try switching from 24 V to only 5V.

Greetings, Sebastian

[Warichet]

@Stefan

24 V is a fairly high value ... although the given values for the allowed voltage for reeds is often significantly higer, you will get quite some trouble concerning the stored charges within your cable.

OK, fine

There were several posts concerning this issu from StefanW

Thank you for the pointer, interesting reading.

@Sebastian

it could help to change your power souce from 24V to 12 V

OK, point taken.

Does the UK/S has dedicated power sources for contacts and own power supply?

No, it's a multipurpose power supply, also used for devices needing external power, but no problem to add/change if required.

In this case it could be interesting to try switching from 24 V to only 5V.

5V ?!? but that's outside the specs of the UK/S. Any experience with a UK/S running 5V on the Reeds ? no negative effect on distance ?