Someone hooked up our new honeywell thermostat and it did not work properly, only worked when you turned the fan to auto. We do not have a fan. We only have heat, boiler, what is called gravity heat I think. The person who hooked it up had one wire going to the Y terminal and one going to the G terminal. After finding out that the G terminal controls the fan I decided it was hooked up wront. So I hooked up the wire that was going to the y term. To RH and the wire that was going to G to W is this o.k.
Will this cause a problem?

<Moved from Elec and Lighting>

For a two wire heat system and no fan, use W and Rh would be correct.

Will this cause a problem?

Yes. Your utility bill will increase due to the heating system working. :D