Installing booster fan via relay switch from Microwave fan wiring

[MisterMateo]

Hello,
I am installing a new over the counter microwave that also functions as a vent hood for my oven. The microwave has a 300 CFM fan that allows me to install a 6" vent pipe that I can run up my wall and into my attic and from the attic to the roof or the side of my home. The length of piping needed is about 15 feet or less and falls within my installation guidelines.

As I was prepping for the install I was thinking it would be helpful to install another "booster fan" inline with the vent pipe in the attic to increase the effectiveness of the ventilation. I am also installing a damper as well.

Here's where I am stuck. I was planning to somehow run the wiring from my microwave fan through a current sensor switch which in turn would switch on the booster fan simultaneously. The microwave fan has two speeds, but I would not require two speeds on the booster fan, but would like it to turn on any time the microwave fan is turned on. This would only help vent the air as I know that most OTR microwave fans are probably marginal at best at really doing the job. I understand this is a common method used on dryer vents.

Another option I am considering is to remove the microwave fan altogether and connect the booster fan directly to the wiring chasis in the microwave or run a similar relay as in the first option. I can install a nice booster vent up up to about 480 CFM, and would also include my own high quality damper to avoid back flow of cold air. I am concerned about wiring directly from the microwave to the booster fan, since I could void or damage electronics in the microwave by having it directly linked to the booster fan. Removing the fan in the microwave would lessen noise and yet provide a better flow of air by using a slightly stronger fan that would be located about 5-6 feet above the microwave in my attic.

Here is an example of the type of booster fan I am considering. Better quality than a typical booster fan you would find in large box stores. If this system works, I would like to do the same to my dryer and bathroom vents as well.
https://www.fantech.net/FG-6M_enus-40466.aspx

Thanks in advance for any feedback you may have.

 

[AnalogKid]

If that is the fan from you microwave, then the warranty already is blown. If you were going to run the fan wiring to a current sensor, why not just wire the external fan in parallel with the internal fan? Set the microwave to low speed, measure the fan wires to find the two that are powered, and parallel onto them.

Wait. Rethinking this, whatever is controlling power to the microwave fan might not be overrated enough to handle two or three times the load. Better to get an AC coil power relay and wire it in parallel with the internal fan, then power the external fan through its contacts.

ak

 

[MisterMateo]

AnalogKid,
thanks for your reply. Your train of thought was the same as mine. Originally I was planning to parallel in the booster or secondary fan, but after considering it, realized that the microwave wiring was not designed for the current of two fans.

For this reason, I am considering an AC current switch sensor relay that will trigger the secondary fan that is wired independently. I'm not an electrician, but I think we are both talking about the same thing. You mentioned using an "AC coil power relay". I assume this is the same as an AC current switch which would trigger the secondary fan when it detects the power from the original fan wiring as it is turned on. I have included a photo of one such device below that may work as long as the amperage of the original fan wire is within the range specified on the switch.

 

[KeepItSimpleStupid]

It's unlikly, but possible that the fan is DC or even low voltage AC. For now, I'll asume that you have a Neutral, Speed 1 and Speed 2. The current sensor can go in the Neutral lead. The sensors sensitivity can be increased by using multiple turns.

The bigger problem is sensitivity. I suspect the fan's current rating has to be small. This sensor https://www.nktechnologies.com/current-sensing-switches/as0-current-sensing-switch/ would work up to (.32*120) Watts or aprox 40. This with a minumum current of 3 mA you can likely pick up the current of a lamp.

It may be pricy. It will also require power either powering with 120 VAC or 24 VAC/DC

No matter how you look at stuff, you still have to pass wires out of the microwave. You can't use the microwave cord because of the max input and you can't guarantee the minimum value either. So let's face it, you'll have to modify the micrwave just to access the wires. In the case of the unit I selected, it's not likely suitable to drive a fan directly because of the Solid state output.

I like AMP CPC connectors, but they may be to big,

You can do the industrial thing and use DIN rail construction and/subpanel to mount a 24 VAC energy limiting transformer and contactor for your fan. You would need 4 wires from this box (24 VAC & return) and the contact closure (2). 24 VAC does not have to be in conduit if energy limited,

There is a spacial class of a transformer that is inherintly energy limiting It will survive a short on it's output.

You may have to providefor a solid/stranded junction box between the microwave and the wall.

Witht he right parts, it's sound. But it will cost you a lot more than expected.

==
4" booster fans do exist,

Is the dryer gas or electric?

Although not as effective and not really recomended unles the lemp is a LED, monitoring th eoutput of a lamp may be effective.

==

There is a wide variety of sampers available, some better than others. Some would be installed at the exit on the inside.

==

I found that a delay on break timer works well for the bathroom. The fan stays on for 20-30 minutes after the fan is turned off.

 

[MisterMateo]

Keepitsimplestupid,
Thanks for your response
Yes, this idea may turn out to be about as expensive as the microwave, but I am still interested in trying it out.

I'm pretty sure the fan is AC and not DC.
I've attached a photo of the microwave fan label and diagram.
The fan has 5 wires:
2 wires for capacitor
2 wires for fan speed
1 return wire (white)

These are very small gauge wires. I would have to splice into the white wire to allow it enough length to exit the microwave and enter into the wall electrical box where I will have the sensor switch located as well as additional wiring going to the extra fan.

A second option is to leave the original fan out and connect to the 5 pin male connector in the microwave with a purchased 5 pin female connector that would do the same thing, but would trigger the larger fan in the attic to reduce the overall noise but provide better venting. However, I'm concerned about what I would do with the capacitor wires in this case, since they would not be connected to a capacitor if the original microwave fan is removed.

You can do the industrial thing and use DIN rail construction and/subpanel to mount a 24 VAC energy limiting transformer and contactor for your fan. You would need 4 wires from this box (24 VAC & return) and the contact closure (2). 24 VAC does not have to be in conduit if energy limited,

I don't follow you here. I'm not too experienced with electrical unless its wiring in basic lights and outlets, etc. "DIN rail and subpanel" is terminology that I'm not familiar with, but I will look into it.


Here is a photo of the specs label of the microwave fan. It looks like the Amperage is 1.2 to 1.6. I've also attached a wiring schematic that I found online. The wiring diagram is for a dryer, but would be similar to what I would do with my microwave fan.

Wiring diagram idea:

 

[KeepItSimpleStupid]

I/O modules

There's a whole family of these sorts of modules with logic supplies of 5. 15 and 24 VDC.

https://www.farnell.com/datasheets/1796202.pdf

These are designed to be mounted on a backplane. Industrially, this is how the presence of AC/DC is detected and reduced to a lower voltage. Right now, I'm not saying this is suitable.

--

In the high sensitivity current sensor case, all you have is a relay and a 24 VAC transformer which would have no trouble being in the attic.

 

[KeepItSimpleStupid]

Put the sensor in the microwave. So, you are at 1.2A, so two turns should work on the sensor you found.

==

EDIT
Here https://publicphoto.org/technology/...panel_automatic-fuses_din-rail__3460img_1846/ is an exampe, probably not the best example of DIN rail construction, but it's an electrical erector set.

 

[MisterMateo]

Good idea, Keepitsimplestupid

Would two turns on the sensor double the amperage? I think the switch I was looking at has a max of 2.5 amps. The low setting on the fan is probably 1.2 amps and the high setting on the fan is probably 1.6 amps (If I understand the label on the fan - see photo in previous post).

Thanks.

 

[AnalogKid]

DIN rail sounds complicated, expensive, and large.

1. Refering with the current sensor device, the output switch rating is 2.5 A max. That is the power level you need to watch for the external fan. The sensor can handle up to 40 A. Each turn through the sensor increases the current the sensor sees. For example (you are correct about reading the fan label) with white fan wire going through the sensor port once, the sensor will see 1.2 A in low speed mode. If you loop the wire through two more times for a total of three windings inside the port, the sensor will see 3.6 A when the fan is drawing 1.2 A. This lets you get low current devices up into the sensor's reliable detection range.

2. The upper dryer wiring drawing (3-phase) is incorrect. If the dryer heating elements are properly matched, there will be no current in the Neutral. Pick any one of the three phases legs for the sensor.

3. While the current sensor probably is the safest way to deal with the energy levels and specialty connections inside a dryer, I think it is overkill for a vent fan and unnecessarily complex. Somewhere inside the microwave is the power source point and return point for the fan circuit. You can wire a relay coil in parallel with the overall fan circuit and your booster will come on no matter which speed is selected. For this I suggest a simple SPST relay, one with a 120 VAC coil and 120 VAC-rated contacts. I don't know what country you are in, but these will work nicely:

https://www.digikey.com/product-detail/en/LY1F-AC110/120/Z782-ND/126834

https://www.digikey.com/product-detail/en/HL1-HTM-AC120V-F/255-3633-ND/3885790

You can wire to it with Faston terminals, solder directly, or buy a mating socket and solder to that.

ak

 

[KeepItSimpleStupid]

Analog has the general idea. The sensor is pretty cool. 3x turns would be fine. Generally you can find some hole that you could put a grommet/ underwriters knot to bring a small cable out safely. Attach stranded wire to a pigtail with a connector at the end and your own plastic junction box to thermostat wire. You can likely find a hole here and there inside the microwave to mount the sensor inside.

These https://www.digikey.com/product-detail/en/206060-1/A1300-ND are actually my favorite connectors, but they are big and you have to buy all of the parts separately, housings, pins, strain reliefs (multiple sizes are available) including a crimper. The pins are available for solder tail, I think. You really should not crimp solid wire. in general unless designed for it.

You could just use connectors and strain reliefs and mount the connector on a flange of some sort. A underwriters knot is a special kind of knot. You loop one wire and then loop the other wire through the made loop. The wire won't pull out of a hole.

I like the sensor itself and the general idea as long as it isn't too expensive.

This https://www.zoro.com/functional-dev...gclid=CMznu82M5cUCFVMXHwodzV4AQw&gclsrc=aw.ds sort of transformer does not need a low voltage fuse or even a small primary fuse. These are typical HVAC transformers. Class 2 generally means <=24 V, and 100 W and energy limited. The reason why your doorbell and HVAC don;t need conduit.

So, a transformer and a relay/contacor mounted in a junction box would be fine. It gets messy. There are enclosures with a 1/4" aluminum plate at the bottom so everything is mounted on that.

The top right relay in this series https://www.mouser.com/ds/2/357/725 Spec Sheet-1809.pdf is about <$25 and the wires are "finge safe". When you have 120 VAC and 24 VAC near each other physical separation is a requirement. Note the DIN RAIL stuff again.
When you use DIN terminals, you can have the input and outputs totally separated and have all the wire rated for 300 V in most of the enclosure.
So you have terminals for N. L and G. G terminals are special blocks that connect to the rail and terminals for the sensor. That way ther eis no confusion as to where the wires go. The box is small enough, but it makes a really noce professional install.

The electrician could wire directly or just wire to a 120 V outlet nearby. All sorts of options are possiblle. The stuff that I did industrially was wired direct with smaller fuses within the box itself. Maybe if I did it again, I would make one a circuit breaker. Nearly everything in the box was 24 VAC.
DIN rail basically means you can get away with 2 mounting screws/rivets.

and then mount a DIN mount transformer (they may exist) and at least 5 terminals and 4 end sections.

If your in the US, I MIGHT be able to make something for you. Consider, your other things as well. You could use one transformer for all and one box, but also consider the dangers of "what if" the booster fan doesn;t turn on. Since two items ar ein the attic, the controls could be there. The dryer system could be separate.

The dryer circuit does show a 3 phase and single phase. Dryers are wierd these days. There may be a drum lamp you can use. The dryer could be gas or electric and 40 A is probably OK,unless 40 A exceeds the surge rating. The starting of a motor could take 4-5x the operating current. Fancy dryers and washers nw use a brushless DC or 3 phase motor internallly with single phasse input.

I like playing devils advocate and I may make things more complicated at first and finally whittle them down. I do like things to be serviceable and reliable. Unfortunately, that comes at a cost. At work, I never wanted to see something I designed again and I used re-useable and modular parts. Some stuff was still in use 25 to 30 years later.

==

Aside:

I don't find DIN rail stuff to be expensive. I have a router at home mounted on DIN rail and I have an automation system ready to go mounted on about 5 feet of DIN rail. It contains two power line nterface for UPB, Insteon and X-10, the automation server, a DXS wireless receiver, An 8 way dry contact block. Eventually it will interface to a wirelss dorrbell that uses security type wireless module (DXS) and a water recirculator and hopefully an outdoor light using UPB. Eventually, I should be able to turn the ligh and recirculator on with my phone. A wireless motion detector will be installed in the bathroom for the recirculator. The recirculator in the kitichen will have to me manually turned on via a wireless X-10 switch and that same X-10 switch will operate a light. There is an xmitter in one vehicle which could be a programmable Home Link system. For the other vehicle, I'd rather the call phone to be bale to turn on the light. These are my initial plans.

As part of other upgrades, there is the freezer door turning on a lamp and/or notifications of low temps to the cell. I'd also add notifications of a PERS (Medical alarm) etc. Then I might move to blinking outdoor lights when the PERS is activated.

 

[KeepItSimpleStupid]

I'd like to know where you found the current sensor. I like it.

 

[MisterMateo]

Thanks for all the great advice, both AnalogKid and KeepItSimpleStupid,
I really appreciate it!

I picked up some parts today and will need to order the current sensor online. To answer your question KeepItSimpleStupid, I found the current sensor from Suncourt. I don't think it is the best quality because it is so cheap, but it should be an easy change if it dies on me.

I already have a electrical box directly behind the microwave that will carry the 120V to the booster fan in the attic. As AnalogKid suggested, I tried to locate the wire that is direct to the microwave fan, but was not able to do so unless I broke a seal on the cover. I prefer not to do that so i am going to clip the white return wire from the fan and solder on about a foot of wire that will extend from the microwave case and enter in the a small opening in the wall to an electrical box that will hold the current sensor switch. The 120V from my main power will feed into the same box and continue up the wall into the booster fan. I prefer to have all the 120V Romex cable in the wall and not exposed behind the microwave for safety reasons.

Thanks again for the help. I've attached photos and diagram...let me know if you see anything wrong with the plan.

Photo of where microwave will be installed. Large vent in wall opening and electrical outlet box that feeds power to an outlet in the cabinet above:

I will add another box below the first, but on the other side of the stud. This is where I will place the current sensor switch.

Quick diagram of the wiring. (Wire from first box to the microwave plug in cabinet above not shown in this diagram)

Hope this makes sense!
Thanks again for your responses.

 

[KeepItSimpleStupid]

BTW, KISS works for the log name,. I just like to suggest, not force my views unless there is a severe reason not to.

Personally, I'd prefer to put the sensor in the microwave and have a potential free and/or low voltage signal exit.
So, another option is this power supply which is designed to go into electrical fixtures, but it's 24 VDC out and therefore you would use a 24 VDC coil relay. It has drawbacks too.

So, stuff like an easily disconnectable connector.

My method the same thing (but better in terms of keeping the 120 VAC contined) The penetrations outside of the microwave are 24 VDC and not at line voltage. You would also have plenty of room for a transformer back there too.

The only advice is to make sure your penetrations use a grommet that hopefully will not degrade with heat. silicon grommets are available from Mcmaster -Carr e.g. http://www.mcmaster.com/#silicone-grommets/=xdxbps

Teflon insulated wire by the foot is available here: **broken link removed** It has very good temperature and abrasion resistance. You may have to do the same for your cover plate.

What I could suggest there is to mount he current transformer on the cover plate and use the grommets there too.
Then pigtail the current xformer with stranded wires that you wirenut to the building wire.

Furthermore, the big reason I don't like your method is you have an exposed 120 V wire not in conduit or protected with an outer insulation. Not sure if Teflon qualifies. I can also argue that with one side disconnected the motor would act as straight piece of wire and you could get a shock if your connected to ground. The kictchen should have a GFCI. I don;t know if GFCI/AFCI's are mandated for kitchens. AFCI is an Arc Fault Circuit Interrupter. It looks for the signature of a loose connection rather than a leakage path to ground.

I don't think your way would pass inspection. My way, I think, would as long as you don't bury the xformer/relay and drywall over it.

So, I'm suggesting some sort of flush mounted junction box.. The AM series here http://www.ctiautomation.net/Allied-Moulded-Enclosures.htm is way out of line, but a similar idea.

This **broken link removed** might be more suitable.

I was trying to find a right angle connector that would be easy to work with.

AGAIN, this is where DIN rail construction starts to shine, but I still don;t have a great way to make the pigtail connection to the microwave.

Then the only thing to worry about is the insulation rating for the 24 V and 120 V wires have to be 300 V and/or separation or physically impossible to touch.

 

[KeepItSimpleStupid]

I hate these **broken link removed** spec sheets. I does say the switch is for AC, but it doesn't mention if the actual switch is solid state. Basically,I know more than they do and they have a specific installation in mind.

This https://www.workaci.com/catalog-new/mini-2 is like a real set of documents.

 

[MisterMateo]

Personally, I'd prefer to put the sensor in the microwave and have a potential free and/or low voltage signal exit.
So, another option is this power supply which is designed to go into electrical fixtures, but it's 24 VDC out and therefore you would use a 24 VDC coil relay. It has drawbacks too.

So, stuff like an easily disconnectable connector.

My method the same thing (but better in terms of keeping the 120 VAC contined) The penetrations outside of the microwave are 24 VDC and not at line voltage. You would also have plenty of room for a transformer back there too.

The only advice is to make sure your penetrations use a grommet that hopefully will not degrade with heat. silicon grommets are available from Mcmaster -Carr e.g. https://www.mcmaster.com/#silicone-grommets/=xdxbps

Teflon insulated wire by the foot is available here: **broken link removed** It has very good temperature and abrasion resistance. You may have to do the same for your cover plate.

KISS,
pardon my naivete, I think I followed most of what you have said here. You are right about the concern over a 120V exposed outside the microwave. What I need help understanding is how I would connect the 24 VDC coil relay inside the microwave. I am not familiar with it, or how it works. Are you saying that I would run a line (24V) from the coil relay (inside the microwave) and into the wall, via a round opening in the cover plate of outlet box? I understand the grommet would protect the sheathing on the wire as it enters the cover plate of the electrical box. The next part I'm confused on is the transformer. If I understand correctly, the wire entering the wall is DC current. When this connects to a transformer, am I stepping up the direct current and running this direct current directly to the booster fan? Need some help on understanding this part.

I can see how the lower 24 voltage would reduce my risk in case of a spark, etc. I could also replace the refrigerator outlet with a GFCI or AFCI outlet, since it is on the same 20amp circuit as the microwave. A great idea there. I have a GFCI outlet on my counter outlet circuit, but not on the microwave/fridge circuit.

Also want to thank you for the teflon insulated wire link...a huge help. I visited all the big box stores today searching for something like this to no avail...that was a life saver. Thank you.

I purchased some flat metal cover plates that include a water seal to cover the two outlet boxes in the wall. Of course a small hole drilled in the center would negate most of that, but they looked like they would help protect against any humidity/water vapor that could come from the microwave or from vapors on the stove below. Placing a grommet in the hole would be a big help too. If I decide to go with the 24VDC, which I will probably do, then I will likely need a larger box, correct?

The transformer and the 24VDC are the components that are new to me. Perhaps with a little more coaching, I'll understand how it can be done. Just cant see how I would connect the 24 VDC coil relay in the microwave. Would it require me to cut off the plastic 5 wire connectors on the internal microwave fan and replace it with the relay? Or, am I just cutting the small white return wire on the fan and connecting that to the relay? That's where I get lost. I also would need help understanding the transformer setup.

Thanks for you feedback. Valid points and I think I'll use your idea, once it's clear to me. Best way to insure against risk is to avoid it altogether. Getting this to pass inspection is key. I will have the city out to inspect everything when done. (They would be coming to inspect a skylight addition I made in the kitchen, but it would also include the new exhaust vent set up).

 

[KeepItSimpleStupid]

The sensor can only switch AC so we have to nix the idea of the DC power supply. My fault. the devil is in the details.

Here goes for part 1. Mount the sensor inside the microwave. You then have to bring out two wires or a cable and satisfy class II wiring. Those two wires are just the contact closure from the sensor.

I'll, sort of refer you to here: https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=4&cad=rja&uact=8&ved=0CDMQFjAD&url=https://escventura.com/manuals/sola_introNECclass2_rg.pdf&ei=-S9oVcfxAoG2sQXNjYHgAg&usg=AFQjCNFja1NF30SY4L1OtMRn9A44MzVp4w&sig2=BEGTWneLd_wwXmmH3RVY1g&bvm=bv.93990622,d.b2w

==

The NEC code can be read online for free with registration. You can't copy/paste or search for info excpet by section #'s if I remember right.

==
So, the point is to get around the don't modify the appliance, so connecting it to the input power source is an option.
So, a slight modification would destroy it's UL listing, so that gives you two choices:

1) In line before it even gets to the microwave
2) Current to the fan. the neutral is used because the voltage to ground is low or near zero and therefore breakdown is less likely.

You want to make the change totally reverseable to keep the microwave warranty which is unnderstandable.

Common sense says stranded wires and your basically wiring a doorbell. it might get a little warm and it might have some moist air nearby. Rubber grommets don't like heat, they crack.

You want to stay out of plenum air spaces and use wire insulation that won;t burn. Teflon (PTFE) insulated wire is actually used for fire alarm signaling, so your kinda looking at alarm and security cables, not "hook-up" wire.
See https://www.generalcable.com/NR/rdo...1_Carol_Alarm_Sec_Brochure.pdfec_Brochure.pdf

Ideally, you'd like a connector mounted to the microwave.

The whole point is to use wire for the intended application and 12 v automotive wire won't work, there's hook-up wire, appliance wire, building wire (THHN, THWN), security wire, fire alarm wire etc.

So, I'm thinking you can get away with two twisted (using a drill) Teflon insulated wires with an underwriters knot with a silicon grommet. For further protection, you could put it in a fiberglass sleave. Hand made has these as well.
terminate in a connector of some sort. I don't know how much room you have.

Teflon insulated wires in a fiberglass sleave, I THINK, would satisfy the code guys. Will they like you modifying the microwave - don't know, but I would have pictures handy.

So, <24 VAC/VDC power limited has been deemed safe to run without rigid protection.

Now, I don't know if your microwave has a plug a plug on it or it;s hardwired, but the point is to get it out safely and easily for service. 16 to 18 AWG is the smallest wire size I would use. The other sensor manufacturer recommends two conductor shielded cable with the shield connected at the receiving end.

It's common to connect shields at one end only.

Does it make sense so far?

I have a hunch that using a sensor like this https://www.workaci.com/content/amcs-0 one, you could get away with not modifying the microwave at all. It;s fully adjustable from 0.32 A to 150 Amps. With two turns you could lower that sensitivity by a factor of 2. Be sure to secure the wires. I could give you a small length of Kapton tape which is like $20 a roll. two turns is about 19 W and 3 turns is about 13 W.

So with the adustibility and 10% hysteresis, I think you can dispense with modifying the microwave and make everyone happy. the sensor is 2x what you picked out. i suppose that using the microwave as a timer would not turn on the fan. if the exhaust fan of the microwave runs continuously and has a detectable draw, you might be "In like flint".

Let this digest for a while. This is why I like to brainstorm with lots of ideas.

Unfortunately, without doing a test you can't know. The cost is 2x your sensor price and if it doesn't work as expected, you can always use it in plan B.

Your thoughts?

 

[kinarfi]

Here's an idea for you, when I worked at a power plant, construction, they had a current sense relay that when tore apart, is was nothing but a reed switch and we would take one of the power leads to the device (your microwave) and wrap it around the sensor a few times to get enough magnetic field to pull the switch in. Then that closed relay signal went to another controller. I don't know for sure if just the current for the fan in the microwave would be enough to pull the reed switch in, it would surely pull in when the microwave was running and the reed switch could be in the switch box ahead of the outlet, leaving the microwave untouched.
You could use that closed contact to operate a relay or scr to power the aux fan.
Not sure if the reed switch contacts would chatter or stay closed, I may experiment with this today and if I do, I'll let you know.
Jeff

 

[KeepItSimpleStupid]

kinarfi:

Over the range micros have controls to run the exhaust without the oven running. You can typically use the oven as a timer too, so therefore there should be some point where the current trip point is slightly less than the current the fan draws on low. The trip point should not trip if the oven controls are used as a timer. Dunno if the hood has a light.
That's why I'm saying maybe it will work on the power input to the microwave.

 

[MisterMateo]

KISS,
I've attached some photos of the microwave fan and the location of the wire that connects the microwave to the fan wire cluster or connector.
I'm trying to understand how i would loop the wire to the coil relay you suggested. Here are the methods of how I understand I would connect the coil relay.

Method #1:
Clip the white 22 awg return wire that is connected to the fan and solder on an extension that would loop 2 or 3 times through the coil relay. This obviously would void any warranty...but it would only be on the fan and not the microwave. Another option would be to insert a wire into the connector of the microwave fan where the white wire exits the connector. I could drop a little solder in the small hole of the connector to hold it. Essentially it would be a pig tail where the white wire exits the connector on the microwave fan. This would not require I cut any wires.

Method #2 (unlikely)
Connect the relay coil to the internal wiring of the microwave before the fan connector. This is likely not an option because the space is limited and I would have to remove the outer shell of the microwave which is sealed.

Method #3
Remove the fan altogether. The new fan i want to install is a stronger and more quiet fan and would work well enough on its own. This would reduce noise when the fan is on and may allow me to connect a relay directly onto the connector inside the microwave. I would just have to find a matching female end of the connector that came with the microwave. I'm not sure how I would do this since the fan has 5 wires...two for the capacitor, 2 for low and high speeds, and then the white return wire.



See photo below of the microwave fan connector.

Below is a photo of the other end of the connector inside the microwave.

 

[KeepItSimpleStupid]

I was trying to find the connector without any luck.

The terminals are usually removable with the right tool. e.g. https://www.molex.com/webdocs/datasheets/pdf/en-us/0011010168_APPLICATION_TOOLIN.pdf

and

**broken link removed**

If you had a connector in hand, you could re-route that particular pin to say a 1 or 2 pin connector and lengthen it in the process.

To put it back un-scathed, you have to remove the pins again. I've never done it, but destroying the single pin housing (i.e. hot razor blade) may save the pin better.

Better pics, the pitch and dimensions or a known dimension in the pic and any identifying marks.

As usual, the manufacturer's keep the removal tool dimensions "secret", so you buy their tool. Delphi has a fair number of removal tools too.

Generally, you have round and flat and front or rear release.

The 745512 here, https://www.jameco.com/1/3/amp-connector-tool, is a ridiculous price, but the dimensions of the part numbers are in the datasheet.

the 305183 is a really nice tool for Circular connector pins.

Some extraction tools, like for D-connectors have really limited life.

These would be known as a wire to wire connector. JST, AMP and Molex are prominent brands.

Not having a dial caliper makes identifying more difficult.

Any identifying marks would help. The little blue things are common with delphi connectors.