2 Speed Fan

[Tw1zzel]

Hi.I have installed a heat recovery unite (HRU) which has a 2 speed fan lo, hi, can be
controlled by a 2 way light switch. Now the problem,I have been asked to fit
pirs in 2 Ensuite bathrooms to run HRU, on the pir is 2 rows of 3 connections 1st row live, neutral,sw. 2nd row n/c,c,n/o with one pir it will work lo speed on n/c when some one walks in to bathroom it switches from n/c lo to n/o hi. Now I need to add a 2nd pir with same set up as fist going to the same HRU this is where i'm stuck,I have been told parallel common to common and n/o to n/o but if I do this will it not mean when one pir is activated it switches from n/c lo to n/o hi and the other pir is still in n/c lo?. Thanks for any help. 

 

[ProDave]

If this is like the HRVU I installed it has just TWO wires to the Hi / lo switch.

So it's an On / off switch.

So you connect to the C and NO on the relay. You don't have anything connected to the NC contact.

So it's true that you just connect the two C's together and the two NO's together, in parallel, and then either PIR will trigger it to switch to hi.  You can also still have the manual switch connected in parallel so you can manually switch it to hi as well, e,g when cooking.

 

[Tw1zzel]

test

 

[Tw1zzel]

Thanks. This unit has trickle speed on all the time and then you can switch to boost speed you can not have trickle and boost at same time or the motor will burn out.so like a light switch you go from L 1 to L 2, if L 1 is like n/c and L 2 is like n o how can no connection to n o work boost speed and disconnect from n c ?

 

[ProDave]

Ah I see, it is actually wired as a changeover switch.

The only thing I can think of is substitute a relay for the switch, using it's changeover contact.

Then you can switch the relay coil from any number of single pole normally open contacts in parallel, which can be PIR sensors or a manual override switch.

 

[Sharpend]

Which make and model have you installed?

With the ones I have done you wire back to the panel, is there no way of wiring the PIR back to the panel using the terminals for the boost? If I remember correctly the panel did the change over itself once signal received from boost switch?

 

[Tw1zzel]

  HRU 100 

 

[kme]

I`m with Dave here - run the PIRs to a relay, and use the changeover contacts of the relay to run the fan.

Safest & easiest, without knowing the specifics of the unit.

 

[ProDave]

Here's the manual http://www.vent-axia.com/files/pdf-downloads/435308.pdf

It does need a changeover switch so a relay remains the only way I can see of it working from two switches.

 

[Tw1zzel]

Thank you, this is what I was thinking ( I'm just the maintenance man) . Now where do I get this relay from?  

Just thinking this relay needs to have a timer built in to it 

 

[ProDave]

Thank you, this is what I was thinking ( I'm just the maintenance man) . Now where do I get this relay from? 

Just thinking this relay needs to have a timer built in to it 

http://cpc.farnell.com/finder/38-51-0-240-0060/relay-screw-term-6a-240vac-dc/dp/SW03614

Or one of these with a suitable screw ternminal base http://cpc.farnell.com/omron-industrial-automation/my2-220-240acs/relay-dpco-220vac/dp/SW03476

 

[Tw1zzel]

Thanks, I was thinking of this http://www.ebay.co.uk/itm/200731948280?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Then I will need a box to fit it in

 

[ProDave]

Thanks, I was thinking of this http://www.ebay.co.uk/itm/200731948280?ssPageName=STRK:MESINDXX:IT&_trksid=p3984.m1436.l2649

Then I will need a box to fit it in

No that's way off the mark.

Just one of the relays I linked to.  You will still need a box, but a 1G or possibly 2G box with a blank plate will do.

 

[Tw1zzel]

No that's way off the mark.

Just one of the relays I linked to.  You will still need a box, but a 1G or possibly 2G box with a blank plate will do.

I will need a timer too

 

[SLIPSHOD & SLAPDASH]

Maplins do a similar relay to that for less thana tenner

http://www.maplin.co.uk/productsearch?criteria=timer+relay

 

[kme]

Why will you need a timer?

The PIR units have timer in them - so THEY will hold the relay energised for you.

ALL you need is a relay with 230V coil, and C/O contacts.......

As Dave above, or I`ve used the small Omron plug-in relays, too.

 

[Tw1zzel]

Thank you all, passed info on,now waiting for the bits to arrive. Yes the pir will do the timing I forgot!  

 

[SPECIAL LOCATION]

Hi.I have installed a heat recovery unite (HRU) which has a 2 speed fan lo, hi, can be

controlled by a 2 way light switch. Now the problem,I have been asked to fit

pirs in 2 Ensuite bathrooms to run HRU, on the pir is 2 rows of 3 connections 1st row live, neutral,sw. 2nd row n/c,c,n/o with one pir it will work lo speed on n/c when some one walks in to bathroom it switches from n/c lo to n/o hi. Now I need to add a 2nd pir with same set up as fist going to the same HRU this is where i'm stuck,I have been told parallel common to common and n/o to n/o but if I do this will it not mean when one pir is activated it switches from n/c lo to n/o hi and the other pir is still in n/c lo?. Thanks for any help. 

Assuming the PIR changeover contacts dry contacts..   {A lot of PIRs are just a changeover relay}

i.e. you have to wire a strap the the 'c' common to get your voltage out on 'Norm Closed' or 'Norm Open'?  then you can do it without a relay I think....

IF YES..

then you could wire the 'NC'-'C' contacts in series with each other to the trickle input

So if one PIR is already working there is no need for the other PIR to apply power as the fan is already on boost!!

and just strap the 'NO' contacts to the boost IP 

see "rough" sketches below...





Guinness

 

[ProDave]

That's excelent SL, a bit of lateral thinking and a neat solution that works without a relay.

Duly scoobed.

 

[kme]

Snap!

Well done bud  :Applaud   :Applaud   :Applaud   Guinness