I'm going to make a little WiFi relay module. I have an 3v. compatible relay and i'm going to use Wemos D1 Mini. I guess an 10amp relay is ok to use for turning on/off an 2.000watt heat fan?
Or should i use transistor for this?
I have two transistors. FQP30N06L and IRF3708. I think booth are N-Channel Logic Level mosfets.
Så what do you guys think?
Relay or one of the mosfets for triggering the heat fan with Wemos D1 Mini?
The voltage powering the 2 KW heater fan would be? A detailed explanation of your goal and a drawing would help. Would the load (heater fan) be AC or DC powered and again what is the voltage? ON a 120 V circuit you are drawing about 17 amps before allowing any headroom and on a 240 V circuit about 8.5 amps.
Ron
Ron_Blain:
The voltage powering the 2 KW heater fan would be? A detailed explanation of your goal and a drawing would help. Would the load (heater fan) be AC or DC powered and again what is the voltage? ON a 120 V circuit you are drawing about 17 amps before allowing any headroom and on a 240 V circuit about 8.5 amps.Ron
I'm sorry...
Here is som more details.
My heater is AC and its 220V. I have no sircuit drawing for now, sorry.
relay would be safest and easiest in this case and fine if you're only turning it on and off at a relatively slow pace. Be careful with line voltage as it can cause death.
Thanks. I think so too. 
Thats my next project
Bjerknez:
I'm sorry...Here is som more details.
My heater is AC and its 220V. I have no sircuit drawing for now, sorry.
Then consider a relay, contactor or since you have a resistive load a simple SSR. I would choose an SSR since then there is no coil to drive. Choose an SSR with a 3 ~ 32 VDC control voltage capable of handling your heater current load plus maybe a 20% overhead. This eliminates the need for a transistor of MOSFET driving a relay coil A simple of 10 amp or 15 amp 240 VAC SSR (Solid State Relay) should give you dozens of hits including some inexpensive off the boat versions.
Yes, you can use a relay or contactor but you will likely need a transistor driver with base resistor to drive the relay coil and a flyback diode across the relay coil. Just make sure the transistor can handle the relay coil current.
Ron
Relay is fine - just get a complete module with all the switching on board and all you have to do it connect it.
looks similar to this:
SSR is fine also - make sure you get the one designed for AC if you go this way.
looks a bit like this... may be different color
Thanks. I allready have the first relay ,so i go for that
The pictured relay is one of these. They come with 03 05 06 09 12 24 and 48 VDC. You don't mention which coil version you have but either way you can turn it On and Off using a simple transistor driver. The 3.0 Volt coil requires 150 mA and the 5 volt coil requires 90 mA. Any common switching transistor like a 2N2222 or 2N3904 can be used to drive your relay coil. Choose your base resistor accordingly.
Personally I would not use one of those relays. They are popular and on millions of relay cards including a few that I have. Switching a few amps they are fine but they never come close to switching their full rated load. You have a 2.0 KW heater powered with 240 VAC according to you. Doing the maths I get 2000 Watts / 240 Volts = 8.333 Amps the same heating element rated for 2.0 KW at 220 Volts = 9.09 amps. Your relay is rated Resistive Load (cosΦ=1) and a heating element is a resistive load, 7A 240VAC in the Form C version and 10A 240VAC in the Form A version making neither suited for your application. These and other forums are loaded with the horror stories of welded relay contacts when these cheap relays are used even below their supposedly rated loads. Just something to consider. The pictured relay is a Form C so below your current demand.
Ron
Thanks.
On mine relay it stands 10amp 240V.
Can i use one of the mosfets i allready have?
No, you can't use a MOSFET to switch the AC line voltage. A MOSFET is for all practical purposes a DC device.
Switching an AC heater On/Off your options are a relay or SSR. You are taking the relay option. All I am stressing to you is the relays (Songle) in the picture and as I linked the data sheet for are low end junk. There was just an issue in this forum about someone using those same relays on a relay board and running below their rated current with a resistive load the contacts kept failing fusing together.
I don't care what is written on the relay, I gave you a link to the pictured relay and offered my opinion of them. Now provide a link to what you actually have because we have played this game before. Looks like is not a good answer. You are comfortable using the relay you have then use it. I wouldn't but that is purely me and I explained why. Relay contacts fail stuck it matters not to me. Just means that your heater won't shut off. Have you planned for over-temp in your temperature control system?
Ron
If you mean can you use a mosfet to switch a relay, yes. This is the circuit
You seem to have started with an image tag and finished with a url tag.
Ron
Haha nice
Thanks for all answers guys
Btw... here is an image of my actual heater and relay:
ok start slow on lower setting and monitor whether the relay gets hot...
I have now ordered some SSR relays. It feels wrong to let an relay that bearly meets specification to run in my basement when i'm not there.
good thinking 
Good move.
Ron