After having had real bad problems with a Paraffin heater I installed electric and bought this little heater. It works a treat and has coped easily with this year's cold weather. It seems to give 3 degrees on top of the outside temperature in an insulated 6' x 10' greenhouse; this is using the first setting on the 1KW button so it has plenty of potential increase to give more heat if required.
The knock over cut out works very well and it is definitely for greenhouse use. Perhaps the previous 1 star reviews were supplied the wrong version? Mine definitely says for greenhouse use and is fit for purpose.
Also a previous reviewer has mentioned the unit does make a certain amount of noise and a little rattle but nothing worth noting for me. It IS NOT silent as the advert on the front says, but it is quiet enough for Greenhouse use, in fact it could be much noisier and still not be a problem.