will relay handel 240v 2kw

Is it ok to use a 2 Channel Relay Board Module Optocoupler like this to switch off/on a 240v 2kw blower heater.
The relays are rated at 10A and (google) at 2Kw a 240 volts the heater will draw 9.07 amps giving 2177 watts, which would indicate that the relay is ok to power the 2kw heater. But i'm wondering about the constant load if running for say 30 mins, would it cause a slow overheat/burnout.
Any thoughts, is there a better relay.

Constant load should be OK. When you switch-on there may be an "inrush" of current, because I think heater-wire has lower resistance when cold.

I'd "feel better" if you had more safety margin, but the relay is rated for 10A and worst case you'll have to replace the relay after some period of time.

You can find higher-current relays, but you might not find a higher-current Arduino-compatible relay board. You can also find solid state relays that can be directly driven by the Arduino, but they tend to be more expensive than a regular electro-mechanical relay.

You can find higher-current relays, but you might not find a higher-current Arduino-compatible relay board.

DISCLAIMER: Mentioning stuff from my own shop... !

Here's a 30A rated optoisolated relay board:
http://www.yourduino.com/sunshop/index.php?l=product_detail&p=478
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And here is a 50A rated Solid State Relay:
http://www.yourduino.com/sunshop/index.php?l=product_detail&p=348

DVDdoug, thanks for the reply.
i've looked at higher rated relays and the price does rise a bit (quite doable though). Thing is i've already made/got a control module that switchers on/off lower power soil heating cables and nothing needs to be changed other than a couple of code variables to power the blower heater as long as the relay can handle the higher wattage. I shall give it a go, whats the worst that can happen ? blow the relay :o

update, terryking228 just pointed me at a 30a relay, which looks like it could be a direct replacement, thanks terryking228.
i'll go with what i have for the short term but order the 30a replacement

DVDdoug:
Constant load should be OK. When you switch-on there may be an “inrush” of current, because I think heater-wire has lower resistance when cold.

No, if that were true you would blow fuses back to the consumer unit every time a 3kW electric fire was
turned on (they take 5–10 seconds to heat up). Heaters are made specifically with nichrome or constantan
wire which has nearly constant resistance across its entire operating temperature range. Heaters can be
treated as constant resistance (unlike tungsten lighting for instance which does have strong inrush current).

I’d “feel better” if you had more safety margin, but the relay is rated for 10A and worst case you’ll have to replace the relay after some period of time.

Indeed - get 16A relays if possible, should not be hard to find.

You can find higher-current relays, but you might not find a higher-current Arduino-compatible relay board. You can also find solid state relays that can be directly driven by the Arduino, but they tend to be more expensive than a regular electro-mechanical relay.

I'm thinking you may need a contactor for that rather than just a relay.

you may need a contactor for that rather than just a relay.

See Wikipedia: Contactor - Wikipedia

A contactor is simply a relay designed for high power or voltage. They are available in standard physical sizes to fit in equipment like air conditioners, ventilation systems, elevators etc etc.

And this is one I'd suggest if the system is driving the blower motor as well as the heater element. I use it to power a 240 volt 1-1/2 hp well pump with another very small relay between the arduino and contactor.

Some interesting and low-cost contactors are available On Amazon

Many contactors have 24 V AC coils and it works well to have a small arduino-controlled relay control the 24V AC to the contactor. Small 24V AC Transformers are often used on furnaces thermostat circuits, door bells etc. Examples HERE

There is a safety concern with using some, not all of these hobby type relay boards, for high current/voltage applications. And the only way you can really be sure of what you're getting, is to have one in hand, and know what you're looking at. And you also need to test it, At 1.5 times the rated current. The relay may stand up to this current, but the question is will the circuit board stand up to it. Does it have enough separation between the circuit traces to be safe. Even a small art between the traces will leave a carbon track. This becomes a resistor, it also becomes a path for electricity to flow. Any carbon track could cause the circuit board to catch fire. Also, the screw terminals on these relays are normally rated between 7A to 8A. To me I would not trust my home or business to this type of relay at high current/voltage. You're better off getting the proper relay/contactor, and driving it with a transistor/2nd relay, At a lower voltage. An SSR, is also a good choice. Just make sure that you use a heatsink and there is plenty of air circulation around it.

MarkT:
No, if that were true you would blow fuses back to the consumer unit every time a 3kW electric fire was
turned on (they take 5--10 seconds to heat up).

Not necessarily. A Type B MCB wil trip between 3 - 5 times the rated current. So a 32Amp for a Ring final circuit can take between 96 - 160 Amps to trip. If you are pulling 40Amps say it will just sit there and get warm.

This is why we do tests on Electrical installations to make sure that the resistance (Zs and Ze) are low enough to provide enough current to trip the MCB between 0.1 secs and 0.5 secs if there is a fault. At the moment (17th Edition Amd 3) for a BS EN 60898 32Amp Type B MCB the Ze value must be below 1.10 Ohms for this to trip reliably

Appendix 3 of the 17th Edition Regulations Amd 3

promacjoe2 - all very good points.

240volts is not something to take lightly. Although one can find specs for proper trace size and placement of those traces on the board, I'd be inclined to keep the high voltage off the board, as well as using a contactor (controlled by a smaller relay, controlled by the arduino) instead of a simple relay (by itself controlled by an arduino), to control anything involving a high voltage, high current, inductor type load.

MarkDerbyshire - good to know people like you are hanging around this forum. Good of you mentioning the IET wiring regulations as a reference. I wonder what was written in it prior to the days when they started using aluminum wiring in homes years ago, had a lot of homes burn down as the contact points to unlike metals in such and similar devices began to corrode, causing the regulations to become tighter taking into consideration a means to prevent that corrosion.

In the OP, the heater is described as a blower heater, so some of the 2kW/240V load will be inductive from the motor. I guess those tiny sugar cube relays would be at their limits with such a load.

thanks for all the replys and info, this is one of the reasons this forum is so good, keeps people like me (who have just enough knowledge to be dangerous) from making big cockups.
In the short term i'll use the relay i have as the unit is needed now but will order either a relay or contactor with a higher amperage. The contactor seems the better but may not fit in the case of the unit/module i have, bit more research needed.

Again thanks for the replys, is appreciated

6v6gt, I strongly concur.

some of the 2kW/240V load will be inductive from the motor

Interesting point!

IF the heater can cycle off with the blower running, and then the blower can later be turned off, all the considerations for running the blower and turning it off apply to the relay/contactor.

IF the heater and motor are permanently wired in parallel, the heater resistance will absorb most of the motor disconnect energy.