I am currently renovating my basement. I plan on running new wiring back to the panel for the basement electric. Since the basement will have an office area and a playroom, I wanted to allow the possibility to have two electric heaters. I plan on using 20 amp rated wiring. Since there is a possibility that both heaters can be operating at the same time, should I dedicate the outlets just for the heaters and run the general purpose outlets on separate circuits or can each room just have the four general purpose outlets together?

You failed to mention some points. It looks like you would like independent thermostats. I think they max out somewhere between 20 and 25 amps.

I would also assume that your wiring two rooms.

The maximum wattage for the heaters assuming 240 V is (240)(20)*0.8

Heating loads are derated 80%. That's the max size for a 20A, 240V breaker.

Doing the calculations the other way. If you had a 5000 W heater, you would multiply by 1.25 and size the system to (5000)*1.25/240 Amps. The upsize to the next breaker size and figure the wirsize from there.

Why not use electric baseboard heat it's much safer. Run the power to the thermostat on the wall first.

Some clarification, proper method of sizing a heat circuit:

A 5000 watt heater at 240 volts draws 20.84 amps. 5000/240=20.84

A heat circuit shall be sized 25% higher than the running load.

20.83 x 1.25= 26.04 amps

A 30 amp circuit can only handle 24 amps, (30 x .8) so a 5000 watt 240 volt heater will need a 40 amp circuit with #8 copper wire. A 40 amp circuit can handle 32 amps (40 x .8).

Without knowing the wattage of your heaters, we cannot size your circuits.

I guess I was originally trying to keep it simple by just using portable heaters and used them only when needed. I didn't think about a permanently wired unit with a thermostat. Not that it's not a good option, I just didn't think about it. Since I was just planning on a portable one, I figured it would just be two small units that put out about 1500W at 120V and have their own thermostat. Do you think this is a bad way to go? The room sizes are approx. 140 sf and 250 sf.

The link to a unit I was considering:

http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?jspStoreDir=hdus&catalogId=10053&productId=100669052&navFlow=3&keyword=200491&langId=-1&searchRedirect=200491&storeId=10051&endecaDataBean=com.homedepot.sa.el.wc.catalog.bean s.EndecaDataBean%406564fdfe&ddkey=Search

Portable heats should be a temporary solution, not a permanent one. People trip, leave them on. The dog knocks it. It's a fire hazzard. It's bad news all around.

You claim one of the rooms is an office. With an unregulated temperature, you won't like it.

The next one is a playroom. If this is for kids, then by all means no!

It's hard to even guess what you really need in terms of heating, but 25' x 10' is a large space to heat with a small heater unless the basement is insulated very well.

You bring up some interesting points. I will look into maybe the more permanent type and use the numbers you are providing above to calculate the size needed.

In the past as an office space I have used a single portable unit when needed and it seemed to do the trick since the basement is pretty well insulated. Not knowing the martket that well, can you point me to a manufacture I should look at?

Kiss is correct, portable heaters are purely temporary. In addition to the issues he brings up, the weak point of any portable heater is the plug inserted into a receptacle.

This connection will usually heat up, and if used for prolong periods, often the heat created at the plug will damage both the plug and receptacle. Popular cause for fire.

I'm not going to recommend or not recommend these,

http://www.cadetco.com/show_product.php?prodid=1004

But the website should answer most of your questions. Come back with any questions. These units offer a lifetime element warranty and you may pay more for that.

Edit: added link

Thanks for the assistance and suggestions. I will do my research and make a determination.

I'll also say that they make programmable "line voltage thermostats". One example is here: Buy Honeywell Digital LineVoltPro™ 8000 Programmable Heat Only Thermostat | Honeywell TL8230A1003 (http://www.iaqsource.com/product.php?p=honeywell_tl8230a1003&product=101013)

Home | Fastenal (http://www.fastenal.com) also has some with a selection tool.

Based on your comments, I have now decided to use electric baseboard heating. Based on the final floor plan, I intend on using:
(1) - Cadet 3 Ft. 750 Watt 240 Volt Electric Baseboard Heater (3.13 Amps)
(1) - Cadet 5 Ft. Electric Baseboard 1250 Watt Heater (5.12 Amps)
(3) - Cadet 4 Ft. Electric Baseboard 1000 Watt Heater (4.17 Amps)

I will also have three thermostats since this will be three different rooms.

20.85 x 1.25= 26.06 amps

So I believe I will need a 40 amp circuit with #8 copper wire.

Is there any advantage to do one 40 amp circuit vs. two 20 amp circuits?

It depends on how you plan on grouping the heaters just how large of a circuit you will need. You can't just bunch them together. If it was me, I would use three circuits of approproate size. That way each one is protected independently, and the thermostat wiring will be much simpler. If you used just one circuit and one of the heaters shorted, you would have no heat at all.

Thanks for your comments. If I put them on (2) 20-amp circuits, I would break one room that has 12 feet of base board on one circuit and the remain two 4 foot runs would be on the other circuit.

Based on the math the first circuit would draw (12.51 amps) x (1.25) = 15.63 amps and the second smaller circuit will draw (8.34 amps) x (1.25) = 10.43 amps.

The wiring for the first circuit is pretty cut and dry since it’s one room and the units are all dedicated to it. I was thinking for the second circuit to run the main feed to a junction box and split off that to the two individual room thermostats then onto the 48” section of baseboard respectively. Do you think this is a problem?

If I use three individual circuits, I am thinking I would use up all the spare slots in my panel since each breaker would take up two slots.