De no ser por el relevo, habría sobrecarga.

De no ser por is a set expression meaning if it weren’t for or were it not for.

So:

• De no ser por el relevo = If it weren’t for the handover / replacement / relief
• habría sobrecarga = there would be overload

It introduces a hypothetical condition: something bad would happen without that factor.

A very common equivalent is:

• Si no fuera por el relevo, habría sobrecarga.

That version may feel more familiar to learners because it looks more like a standard if sentence.

Because de no ser por is a condensed structure built with de + infinitive.

In Spanish, de + infinitive can introduce a condition, often in a slightly formal or written style:

• De haberlo sabido... = If I had known...
• De no estar aquí... = If I were not here...
• De no ser por... = If it were not for...

So the infinitive ser is normal here. It is not a mistake or a shortened subjunctive form; it is a different grammatical pattern.

The fuller, more obviously conditional version would be:

• Si no fuera por el relevo, habría sobrecarga.

Both are correct.

Because the meaning is negative: if it were not for.

Compare:

• De ser por el relevo... → this would not make sense in the intended way here
• De no ser por el relevo... → if it weren’t for the handover / relief

The no is essential because the sentence is saying that without the relevo, overload would happen.

Both are natural, but they differ a bit in style.

• Si no fuera por... is usually more straightforward and common in everyday speech.
• De no ser por... sounds a bit more compact, formal, or written.

So:

• Si no fuera por el relevo, habría sobrecarga.
• De no ser por el relevo, habría sobrecarga.

These mean essentially the same thing.

A learner should definitely recognize de no ser por, but in conversation they may hear si no fuera por more often.

Relevo has several related meanings, all connected to the idea of someone or something taking over.

Depending on context, it can mean:

• a replacement
• a relief
• a shift change
• a handover
• in some contexts, a relay

In this sentence, el relevo probably means something like:

• a change of shift
• a replacement person/team
• a handover that distributes the work

That is why it prevents sobrecarga.

So the exact translation depends on context, but the core idea is that someone or something steps in, avoiding overload.

Habría is the conditional form of haber.

Here it means there would be:

• habría sobrecarga = there would be overload

It is used because the sentence describes a hypothetical result:

• If it weren’t for the relevo, there would be overload.

This matches the unreal or hypothetical condition in the first part.

You can think of the structure like this:

• De no ser por X, habría Y
• If it weren’t for X, there would be Y

Because Spanish uses haber for existence:

• hay = there is / there are
• había = there was / there were
• habrá = there will be
• habría = there would be

So:

• hay sobrecarga = there is overload
• habría sobrecarga = there would be overload

English uses there is/there would be, but Spanish expresses that idea with forms of haber.

Because sobrecarga is being used as a general, uncountable idea: overload.

So:

• habría sobrecarga = there would be overload

That sounds natural in Spanish.

If you said habría una sobrecarga, it would sound more like:

• there would be an overload
• a more specific event or instance of overload

Without the article, the sentence refers more generally to the condition or situation of overload.

Yes. You could also say:

• Habría sobrecarga de no ser por el relevo.

That is grammatically correct.

But placing the conditional part first is very natural because it sets up the condition before the result:

• De no ser por el relevo, habría sobrecarga.

This order is especially common in formal or written Spanish.

In de no ser por, the por is part of the fixed expression. The whole phrase means if it were not for / were it not for / but for.

You do not need to analyse it too literally word by word in normal use. It is best learned as a chunk:

• no ser por alguien/algo = to not be for someone/something
• in natural English: if it weren’t for someone/something

Examples:

• De no ser por ti, no lo habría conseguido.
  If it weren’t for you, I wouldn’t have achieved it.

• De no ser por la ayuda, estaríamos perdidos.
  If it weren’t for the help, we’d be lost.

So por links the situation to the factor that prevents or causes it.

It sounds somewhat neutral-to-formal because of de no ser por.

The sentence is perfectly natural, but it has a slightly more concise and polished feel than:

• Si no fuera por el relevo, habría sobrecarga.

So if you are speaking casually, you might choose the si no fuera por version more often. But the original sentence is absolutely standard and useful to understand.

Yes. The pattern de + infinitive is used quite a lot in formal or written Spanish to express conditions.

Examples:

• De tener más tiempo, iría contigo.
  If I had more time, I would go with you.

• De no llegar pronto, empezarán sin nosotros.
  If we don’t arrive soon, they’ll start without us.

• De haberlo sabido, no habría venido.
  If I had known, I wouldn’t have come.

So de no ser por is part of a broader pattern, not an isolated oddity.