How do I defrost the Samsung RB215LASH bottom freezer?

The defrost water from the melted frost (ice) collects in the bottom of the freezer. If there is no plugged up drain, then you must remove the water manually with a sponge and bucket after a defrost cycle.

You have a problem in the de-frost system. Could be a timer, very common, heat element, very common. Look on line or your owner manual and see what that code is telling you. The average person can not make this repair. Hope it is under warranty.

BA Baker... hello,

Ice collecting on the bottom of the freezer.. is not such a terrible thing...

(Probably means the defrost is working... (merely not EXITING)).

New refrig or unfamiliar refrig could cause deeper analysis...
but if ...

If this is not a new device... and has been happily tending to it's own needs (evaporating well) for a while (months would be re-assuring)...

Then you are MOST probably looking at a clogged evaporator drain... (usually easily fixed by negotiating "WARM" (not hot) through the bottom vents slots of your freezer section.

Looking under your Refrigerator/Freezer... or consulting your owners manual... Locate your defrost "catch" pan...

It should NOT be dusty...

(easily tested: clean paper in tray...
Still clean tomorrow = clogged drain (pan is watered daily).

Close inspection should reveal a tube descending into it.... This is where you will watch for your patiently applied doses of warm water to appear... (near immediate).

It may take several doses... because ice can also have formed over the drain... Be persistent... You will be proud.

Please comment me back... I really like REFRIGERATORS/Frzrs...
few appliances tend to themselves so well (adorable).

Samsung RF4287HABP User Manual

There is a drain tube located under the panel of most freezers. If that clogs up, the auto defrost can't work. The freezer defrosts by evaporating all the moisture out of the compartment. So, check that first. Secondly, a leaky door seal can also cause that problem. You can order door seals online or on Amazon.

Something here should cover your problem.
side by side refrigerator ice on freezer floor YouTube

drain for defrost must be plugged

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If it is a frost free unit the water collects in a well at the compressor , there is a heater element in the well that boils off the water , this is were the fault is.

Check for ice build-up in and around the freezer fan where the blades are, if you can see ice in there (some times it may look like white foam but dont be fooled, it will be ice), the fan will be hitting it, defrost the freezer and check defrost element, (you will have to dismantle freezer section to get to it but reletively simple job) disconect from mains first. Good luck

Frost free fidges are supposed to stay frost free because the automatically defrost regularly. When they do this they may drain water down to the bottom of your fridge. Look for a tray that catches this water underneath the unit. Make sure yo keep it emptied. If you live in a very warm climate you may be getting a lot of humidity inside. There may be a switch that you can change for lower moisture.

probably the defrost drain blocked. remove back panel from inside freezer and melt ice off with hairdryer and follow up with hot water till water flows away freely.
you may find all the pipework iced up and if so you have a problem with defrost system.
an alternative way is to switch off for 24 hours and leave doors open