Vent Axia PIV Unit - Switch live when spur has switch

[Alexkx3]

Hi all,

I am wiring a Vent axia pozidry fan, and am I right in assuming if the spur I am using has it's own switch, I can just link the L to the LS at the fan?

Many thanks in advance.

Best,

Alex

 

[EFLImpudence]

What are you trying to achieve?

The device is a Switched Fused Connector Unit; the cable is the spur.

 

[EFLImpudence]

Second thoughts - the switch is a fused three-pole isolator.

 

[Alexkx3]

Hi thanks for your reply,

I basically want to take from the normal (ring main) wall plug to the switched fused spur and then to the fan. 3A switched fused spur is required, so device can be turned off with the spur. So I have supply of L N (E) that go into the switched fused spur that then goes into the FAN which requires L N LS (E).

 

[EFLImpudence]

LS on fans normally refers to the timer connection but as far as I can see on this fan it is a speed boost function. Is that correct?

Therefore if you connect L & LS it will be on high speed all the time.


Also the diagram does not show the correct Switched Fused Connector Unit (the cable is the spur) as the fuse only protects one of the line(live) wires.

You will need to do this:

 

[Alexkx3]

Thanks much appreciated, yes the instructions are very vauge, the speed boost is controlled internally, and there is no timer, so I'm not sure what the LS is for, apart from jsut been an additional way to turn the device off.

 

[EFLImpudence]

I have only read the instructions.
It looks like the internal settings are to set the permanent speed and the LS when switched on boosts it until switched off?

Either way my diagram is the correct way to wire it.

 

[Alexkx3]

Ah thanks for that, I really appreciate you digging into the instructions. My fault, I kinda skimmed past and went straight to the wiring diagram!

 

[EFLImpudence]

 

[JohnW2]

As a matter of interest ... how can a fan serve 2, 3 or 4 bedrooms "when no ducting is used"?

 

[Alexkx3]

It's not a fan per se but a positive input ventilation system. The idea is it sucks in filtered air from outside, creating positive pressure in the house which pushes the stale humid internal air out through whatever gaps exist in walls/windows/doors etc. Its meant to stop build of condensation and allergens etc Well we'll see if it works.

 

[JohnW2]

It's not a fan per se but a positive input ventilation system. The idea is it sucks in filtered air from outside, creating positive pressure in the house which pushes the stale humid internal air out through whatever gaps exist in walls/windows/doors etc. Its meant to stop build of condensation and allergens etc Well we'll see if it works.

Fair enough - although not that much different from the usual system which pumps the stale humid air out, provided there is a means for some cold outside air to come in to replace it! Either way, in the absence of 'heat recovery' systems, one is replacing (expensively!) heated air with cold outside air, at least during cold periods of the year!

However, my question remains - if there is just one 'fan', how does it suck outside air into multiple rooms without the use of any ducting?

 

[Alexkx3]

Yes, the heat loss is not ideal but hopefully better than my current option which is having the windows open in winter, which still doesn't seem to solve the issue of condensation and my wife's allergies. I'm sceptical as well. Would have gone for a 2 way vented heat recovery system but my flat isn't suitable for it apparently (needs to be better insulated and air tight).

 

[JohnW2]

Yes, the heat loss is not ideal but hopefully better than my current option which is having the windows open in winter, which still doesn't seem to solve the issue of condensation and my wife's allergies. I'm sceptical as well.

Condensation occurs when moisture-laden air comes in contact with cold walls. Getting the room (including the walls) as hot as possible before the 'steam' is produced would therefore presumably help to some extent.

Unless some factors persuade a lot of the moist air to go out of an open window, taking that approach may actually be counter-productive, by lowering the temp of the room, including the walls!

Would have gone for a 2 way vented heat recovery system but my flat isn't suitable for it apparently (needs to be better insulated and air tight).

Fair enough.

 

[pcaouolte]

These units work well when you can't persuade people in the property to ventilate it properly. Fresh filtered air is introduced gently into the property to displace moisture laden air. The air circulates around the property via gaps under doors.

I find that they push air from upstairs to downstairs which offsets the normal rising action of hot air, this keeps the warmest air where most people want it, in the living spaces downstairs. In my experience they have no noticeable effect on heating costs.

They do introduce what might be described as a cold draught on the landing which can be felt when walking near them, most people don't spend a lot of time on their landing and are not concerned about it. They don't produce a cold draught in other rooms.

When the loft space is being heated by the sun they turn up the fan speed to move more of that warm air into the living space. When the loft gets baking hot in the summer they shut down to avoid over-heating the house.