Relays on PCB's

[SkyWalker]

hi guys, would i be correct in saying that the relays found on split/vrv a/c units are Solid state relays? i mean the ones that are solderd onto the boards and generally are "black blocks" looking like this http://www.drillspot.com/pimages/387/38734_300.jpg

[frank]

No, solid state relays are totally electronic with no moving parts.

Mechanical relays are different.

[SkyWalker]

so the relays found on PCB's (generally) are mechanical relays?

[frank]

Generally - yes. A magnetic coil causing 2 or more contacts to make (energised) or break (not energised) - or vica versa depending on whether it's a NO or NC contact.

A solid state relay uses an electrical 'signal' into the 'Gate' to cause the current to flow.
http://en.wikipedia.org/wiki/Solid_state_relay

[SkyWalker]

thanks frank i just didn't know which was generally used, aint got any to hand so i couldn't check, thought i would ask, thanks again

ps i live in Nottingham fancy taking me under your wing?, lol

[nike123]

Solid state relays are generally used in domestic/commercial split air conditioning systems only for speed regulation purpose of AC fan motors. They regulate speed of fan by cutting power supply to fan motor many times per second (pulse width modulation -PWM). Main processor feed them with signal, and hall element in motor gives rotation speed achieved to main processor and it corrects its signal according to remote control settings and processor algorithm to achieve desired speed.
Main reason for its use is because of many off-on cycles which cannot be achieved with normal electromechanical relay.
For all other relay functions it is ordinary electromagnetic relay used.

[paul_h]

It varies between brands. Panasonic used solid state in their splits for a while to power cond fans. They look similar to mechanical relay 'black boxes' but are really thin.
Most have normal mechanical relays (including pana) for large current draw devices like compressors.
I've seen a heap of solid state relays for heaters (lab incubators) though, not domestic.
Mechanical relay is cheaper and more reliable than solid state, SS only used when noise, size or operating frequency is a problem

[frank]

ps i live in Nottingham fancy taking me under your wing?, lol

Are you studying at Basford? assuming you are a student.

[SkyWalker]

thanks paul + nike, i was reading on the net about SSR and noticed they looked familiar but wasnt sure if "splits" used them as i thought i could hear the relays making a breaking, ei "moving parts".

Frank - i will be next year, doing my level 3, did level 2 on night course (was forced to by my employer) doing lev 3 on day release! do you have any involvement at baseford?

[frank]

Frank - do you have any involvement at baseford?

I used to, but now I just support them with providing 'on the job' experience for the trainees.