LL's right to enter for maintenance

I'm a LL of a 8 family building in which i also live in.
Here in New Jersey winter is fast approaching and i always start to prepare for it now by checking everyones weather stripping and chaulking for drafts and wear and tear. And every so often i drain the radiators of water
(its a steam heating system) for proper heating of the units. I inform 2 tenants on 10/9/07 that i and the plumber will be working in their apts. this sat 10/13/07 all day, I did it orally, tonight,10/12/07 at around 8:30pm i went to remind them that we'll be there at 10 am and 1 of them said no that they are not going to be here and that i don't have permission to enter. this is the first time this happens and i don't know why, but. i explain to them that the plumber was coming and that i haven't made arrangements with anyone else so that i couldn't change it and that since i gave them 3 days notice that i had the right to enter to do scheduled maintenance.
IS this right, can i enter even if they changed their minds and with draw their permission, nothing is in writing and its not in the lease yet...lol
will i can into trouble if we enter to do work??
thank you
ojeal@hotmail.com

[OHlandlord]

You should put all Notices To Enter in writing and give them to the tenant. Do not verbally notify a tenant. Make sure you note on the notice that this is mandatory maintenance. You must maintain this system each year or they may be without heat. A tenant may refuse to allow you entry, however, most state laws say a tenant cannot unreasonably refuse entry. Refusal to allow entry can be grounds for eviction in some places (and should say so in future leases).

Since this is for mainteanance of the heating syatem, I would go ahead and enter, leaving a note that says you were there on a mandatory service call to maintain the heating system. Be prepared for the tenant to complain. But you have no notice in writing that states they refused permission, so it is their word against yours if you could go in. They may accuse you of stealing if you enter, so watch the plumber carefully there, even if you know himn well. (You'll be able to say you did.) Usuallu when a tenant doesn't want you in their unit without them being there, they have something they want to hide. The last 2 tenants I had that acted like this were both on drugs! But don't snoop. Stick to just what it says you were there to do. (You never know -the tenant may have a hidden camera set up. If their only video is of you doing just what you were supposed to do, they can't use it against you.)