What solenoid to use?

I live in a windy area and have wondering how to close the house ventilation flaps firmly using a solenoid. eg cooker fans, toilet vents etc. Most would be 6" or 8" pipes out through the outside wall with a flap closing off the flow somewhere along the length of the pipe between appliance and outside.

I want the flap to open when a fan is switched on and vice versa. My problem is how to find / choose a solenoid that will hold a flap open for periods of use and not get so hot as to be dangerous. These would be placed in hidden areas of the building so they must be fairly foolproof. The necessary throw would be 1" - 2".

I have some ex-equipment solenoids but I'm not up to speed enough to know whats safe to use in this sort of situation and what is not.

Any advice on how to proceed will be welcome.

Instead of a solenoid have a look at 'duct damper actuators'.

These come in a range of prices, you can even get small ones for car vent ducts. They are designed to motor open or closed so only require power to change state.

You can also get complete duct dampers with actuators attached.

A very good damper drive actuator is the Honeywell Versadrive. I worked on developing these about 30 yr ago.

**LINK**

If you can find one you will not be disappointed. Honeywell may still sell variants, but not sure if modern ones are the same design.

There are some gravity type flaps set at a slight angle that only open when there is internal pressure. Often fitted to cooker hoods, no leccie iused at all.

DC motor drive is likely to be better and cheaper, small geared motor driving a screw. You can buy complete units on eBay, search for linear actuator.

Generic car door lock actuators are pretty powerful and can be found quite cheaply in various designs and sizes. You need the 5 wire "central" one for stand alone jobs. About a fiver off E-Bay.

I've used them as a powerful solenoid substitute. Around a "long inch" travel I think.

Clive

There's one fitted to my cooker hood. On a gusty day like today it goes:

flap flap flap flapflap flap flap flap flap flapflapflap flap flap flap flap flap flapflap flap flap flap flap flapflapflap flap flap flap flap flap flapflap flap flap flap flap flap flapflapflapflap flap flap flap flap flapflap flap

(repeat ad nauseam)

George

Edit:  the system software took out all my extra  spaces - you'll have to imagine the random pauses between flaps.

G.

Edited By Georgineer on 13/10/2019 12:32:54

Gravity flap with adjustable weight?

Regards Ian.

Thank you to all who replied. A few good leads there and I'm leaning towards linear activator or the car door lock actuator for simplicity. I'll do a read-up and search for sources.

John

Our cooker ventilator, also rattles if the wind is in the right direction.

When we lived near the sea, many years ago, to prevent excess draught burning all the sold fuel overnight, I made up a flap with a weight on an arm, and used this to bleed air into the flue, and limit the draught. Worked a treat, pure guesswork, of course!

Howard

Our bathroom fan came with one built in. The solenoid is very small.

While some (most) ventilation can be positively avoided, do not cover any ventilation designed to provide a draught for fuel burning appliances. As you say you only want to close those with flaps, you may well be aware of the risk of carbon monoxide poisoning.

You could try 2 solenoids with an over-centre mechanism, one solenoid opens it, but the spring or weight keeps it open so the solenoid can be switched off, other solenoid vice versa, but I agree the actuator sounds best

Edited By duncan webster on 13/10/2019 23:59:19

Neil; anything over a force 5 will overwhelm the normal bathroom Louvre fans and make them rattle. I need to provide for the occasional force 9!

Duncan: Wiring one solenoid , maybe. Two of them, no chance! No electrical genius here. A simple actuator seems my best solution. Most seem to be DC.

I have never had one in the hand so to speak. Am I right in thinking that when the power is cut off them that they stay put in that position until re-activated?

John

At least as far as the ones I pointed out, that's correct. Motor drives leadscrew through gears, leadscrew moves pushrod. Applying force to pushrod will not turn motor, too much friction. Think of leaving electric car window open and turning off ignition.

Try googling "belimo actuator" for a wide range of damper actuators - essentially a motor driven crank that turns trough 90 degrees. Other variants are available but looking at ebay at the moment there seem to be quite a few on offer around the £25 to 30 sort of mark.

HTH Simon

John, Simon, thank you, lots of useful info.