Usually, the 240 volt is better. (It is the same as 220) AC means alternating current. The current goes both ways through the wire, first one way then the other. If it is reduced to go only one way, it is called 120v, and if it goes both ways it is double that, or 240. Generally, 240 is easier on wiring and equipment. It also uses the whole phase instead of throwing half of it away, so it can be more economical. It probably won't make much difference if you are just getting the chill off of a small floor. The 240 usually isn't designed to get much hotter, or it might damage the wiring. It may heat up a little faster, but that can be dependant on the system itself and may not matter if you turn it on early enough. I would buy it from the same place you are getting the tile from and have their installer install it with the tile. Then there is no finger pointing ability if it has a problem. If that flooring company can't give you any good reasons to use their 120v version, then go with the 220- 240v.

As a rule of thumb, when you are heating an area over 120sq ft., you will likely use a 240v system(s). Why? Here is the reasoning behind this recommendation:
• Once you have measured the space you are trying to heat (remember to exclude any permanent fixtures from your calculations, such as cabinets or bathtubs, showers, etc., and factor in a 2” perimeter) you will know how much material you will need to purchase from us. 120v systems provide more options for covering smaller areas; similarly, 240v systems provide more options for larger areas.
•As you will note on each flooring page, there is a product link where you can see the sizes available, their respective volts and the amount of amps each size will draw. This information will help you determine exactly how much material you will need.
•No matter whether you are using one or several heating systems, each specially designed thermostat that will power them can handle 15 amps max. More than that and you need to purchase a relay or an additional thermostat depending on whether your use a standard thermostat or 3iE.
•Add up the total amount of amps your heating system(s) will use to warm your area and you will know how many systems and thermostats and you will need to purchase.
•The 240v products use less amps which might help if you have limited space/breakers in your electrical panel.

The more heating systems and thermostats you need to purchase will affect the total cost. If you tried to heat a large area with 120v systems, you would need more material and therefore more thermostats to power them. However, this voltage but would be ideal for smaller areas, such as in a bathroom. Heating a sunroom for example, should be left to the 240v systems to handle.

I have a very cold crawl space under my bathroom, we just had 120 V heated floors installed, but it seems that the floor is having a hard time getting to the temperature set on the thermostat. We’ve waited for days and it never quite makes it but it’s very cold outside. Wondering if he should be used at 240V instead of a 110? any insights?

You need insualtion in the floor under the bathroom or the heat is just going into the crawlspace